CVE-2025-40026

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2025-40026", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.152Z", "datePublished": "2025-10-28T09:32:33.075Z", "dateUpdated": "2026-10-15T22:02:36.361Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:07:08.793Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Don't (re)check L1 intercepts when completing userspace I/O\n\nWhen completing emulation of instruction that generated a userspace exit\nfor I/O, don't recheck L1 intercepts as KVM has already finished that\nphase of instruction execution, i.e. has already committed to allowing L2\nto perform I/O. If L1 (or host userspace) modifies the I/O permission\nbitmaps during the exit to userspace, KVM will treat the access as being\nintercepted despite already having emulated the I/O access.\n\nPivot on EMULTYPE_NO_DECODE to detect that KVM is completing emulation.\nOf the three users of EMULTYPE_NO_DECODE, only complete_emulated_io() (the\nintended \"recipient\") can reach the code in question. gp_interception()'s\nuse is mutually exclusive with is_guest_mode(), and\ncomplete_emulated_insn_gp() unconditionally pairs EMULTYPE_NO_DECODE with\nEMULTYPE_SKIP.\n\nThe bad behavior was detected by a syzkaller program that toggles port I/O\ninterception during the userspace I/O exit, ultimately resulting in a WARN\non vcpu->arch.pio.count being non-zero due to KVM no completing emulation\nof the I/O instruction.\n\n WARNING: CPU: 23 PID: 1083 at arch/x86/kvm/x86.c:8039 emulator_pio_in_out+0x154/0x170 [kvm]\n Modules linked in: kvm_intel kvm irqbypass\n CPU: 23 UID: 1000 PID: 1083 Comm: repro Not tainted 6.16.0-rc5-c1610d2d66b1-next-vm #74 NONE\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n RIP: 0010:emulator_pio_in_out+0x154/0x170 [kvm]\n PKRU: 55555554\n Call Trace:\n <TASK>\n kvm_fast_pio+0xd6/0x1d0 [kvm]\n vmx_handle_exit+0x149/0x610 [kvm_intel]\n kvm_arch_vcpu_ioctl_run+0xda8/0x1ac0 [kvm]\n kvm_vcpu_ioctl+0x244/0x8c0 [kvm]\n __x64_sys_ioctl+0x8a/0xd0\n do_syscall_64+0x5d/0xc60\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n </TASK>"}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H", "baseScore": 7.9, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - Exploitation requires either `KVM_RUN`/`ioctl()` access to `/dev/kvm` on the host or code execution inside a guest running a nested hypervisor; there is no network-reachable path to `x86_emulate_insn()`.\nAC:L - The syzkaller reproducer deterministically toggles the port-I/O bitmap while servicing the `KVM_EXIT_IO` exit, and the guest-side variant only needs a second L1 vCPU to write the bitmap page \u2014 the attacker controls both sides of the window, and nested virt is enabled by default on kvm_intel/kvm_amd.\nPR:L - The attacker needs only unprivileged access to `/dev/kvm` (commonly granted via the `kvm` group or a VMM process), or ordinary code execution inside a guest; no root or CAP_SYS_ADMIN in the init namespace is required.\nUI:N - The vCPU thread reaches the buggy re-check on the normal `KVM_RUN` re-entry path after a userspace I/O exit; no victim action is needed.\nS:C - A guest (L1/L2) triggers corrupted state and a WARN/panic in the host kernel's KVM module, crossing the guest-to-host security boundary, and the aborted emulation also crosses the L1/L2 authority boundary by delivering an I/O intercept L1 never legitimately received.\nC:L - The stale `pio.count`/`pio.size` makes the next emulated `in` take the completion path and hand back data captured during the earlier I/O read on L2's behalf, leaking bounded `pio_data` contents across the L1/L2 boundary; the copy is capped at the 1024-byte `read_cache`, so it is not an arbitrary read.\nI:L - KVM injects a nested IOIO VM-exit to L1 for an access it already performed against the host device model (double execution) and subsequently substitutes stale `pio_data` for a real port read, corrupting guest I/O state in a limited, non-arbitrary way.\nA:H - The un-cleared `vcpu->arch.pio.count` trips `WARN_ON_ONCE()` in `emulator_pio_in_out()` in the host kernel \u2014 a full host panic on the widely deployed `panic_on_warn=1` configuration \u2014 and leaves the vCPU with permanently desynchronized emulation state."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/x86/kvm/emulate.c", "arch/x86/kvm/kvm_emulate.h", "arch/x86/kvm/x86.c"], "versions": [{"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "a908eca437789589dd4624da428614c1275064dc", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "00338255bb1f422642fb2798ebe92e93b6e4209b", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "e0ce3ed1048a47986d15aef1a98ebda25560d257", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "ba35a5d775799ce5ad60230be97336f2fefd518e", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "3d3abf3f7e8b1abb082070a343de82d7efc80523", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "e7177c7e32cb806f348387b7f4faafd4a5b32054", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "3a062a5c55adc5507600b9ae6d911e247e2f1d6e", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "7366830642505683bbe905a2ba5d18d6e4b512b8", "status": "affected", "versionType": "git"}, {"version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "e750f85391286a4c8100275516973324b621a269", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/x86/kvm/emulate.c", "arch/x86/kvm/kvm_emulate.h", "arch/x86/kvm/x86.c"], "versions": [{"version": "3.0", "status": "affected"}, {"version": "0", "lessThan": "3.0", "status": "unaffected", "versionType": "semver"}, {"version": "5.4.301", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.246", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.195", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.157", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.111", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.52", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.16.12", "lessThanOrEqual": "6.16.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.17.2", "lessThanOrEqual": "6.17.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "5.4.301"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "5.10.246"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "5.15.195"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.1.157"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.6.111"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.12.52"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.16.12"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.17.2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.0", "versionEndExcluding": "6.18"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/a908eca437789589dd4624da428614c1275064dc"}, {"url": "https://git.kernel.org/stable/c/00338255bb1f422642fb2798ebe92e93b6e4209b"}, {"url": "https://git.kernel.org/stable/c/e0ce3ed1048a47986d15aef1a98ebda25560d257"}, {"url": "https://git.kernel.org/stable/c/ba35a5d775799ce5ad60230be97336f2fefd518e"}, {"url": "https://git.kernel.org/stable/c/3d3abf3f7e8b1abb082070a343de82d7efc80523"}, {"url": "https://git.kernel.org/stable/c/e7177c7e32cb806f348387b7f4faafd4a5b32054"}, {"url": "https://git.kernel.org/stable/c/3a062a5c55adc5507600b9ae6d911e247e2f1d6e"}, {"url": "https://git.kernel.org/stable/c/7366830642505683bbe905a2ba5d18d6e4b512b8"}, {"url": "https://git.kernel.org/stable/c/e750f85391286a4c8100275516973324b621a269"}], "title": "KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2025-40026", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-10-15T21:56:14.274469Z"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-15T22:02:36.361Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2025-40026", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-10-15T21:56:14.274469Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-15T21:56:15.294Z"}}], "cna": {"title": "KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O", "metrics": [{"cvssV3_1": {"version": "3.1", "baseScore": 7.9, "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H"}, "scenarios": [{"lang": "en", "value": "AV:L - Exploitation requires either `KVM_RUN`/`ioctl()` access to `/dev/kvm` on the host or code execution inside a guest running a nested hypervisor; there is no network-reachable path to `x86_emulate_insn()`.\nAC:L - The syzkaller reproducer deterministically toggles the port-I/O bitmap while servicing the `KVM_EXIT_IO` exit, and the guest-side variant only needs a second L1 vCPU to write the bitmap page \u2014 the attacker controls both sides of the window, and nested virt is enabled by default on kvm_intel/kvm_amd.\nPR:L - The attacker needs only unprivileged access to `/dev/kvm` (commonly granted via the `kvm` group or a VMM process), or ordinary code execution inside a guest; no root or CAP_SYS_ADMIN in the init namespace is required.\nUI:N - The vCPU thread reaches the buggy re-check on the normal `KVM_RUN` re-entry path after a userspace I/O exit; no victim action is needed.\nS:C - A guest (L1/L2) triggers corrupted state and a WARN/panic in the host kernel's KVM module, crossing the guest-to-host security boundary, and the aborted emulation also crosses the L1/L2 authority boundary by delivering an I/O intercept L1 never legitimately received.\nC:L - The stale `pio.count`/`pio.size` makes the next emulated `in` take the completion path and hand back data captured during the earlier I/O read on L2's behalf, leaking bounded `pio_data` contents across the L1/L2 boundary; the copy is capped at the 1024-byte `read_cache`, so it is not an arbitrary read.\nI:L - KVM injects a nested IOIO VM-exit to L1 for an access it already performed against the host device model (double execution) and subsequently substitutes stale `pio_data` for a real port read, corrupting guest I/O state in a limited, non-arbitrary way.\nA:H - The un-cleared `vcpu->arch.pio.count` trips `WARN_ON_ONCE()` in `emulator_pio_in_out()` in the host kernel \u2014 a full host panic on the widely deployed `panic_on_warn=1` configuration \u2014 and leaves the vCPU with permanently desynchronized emulation state."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "a908eca437789589dd4624da428614c1275064dc", "versionType": "git"}, {"status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "00338255bb1f422642fb2798ebe92e93b6e4209b", "versionType": "git"}, {"status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "e0ce3ed1048a47986d15aef1a98ebda25560d257", "versionType": "git"}, {"status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "ba35a5d775799ce5ad60230be97336f2fefd518e", "versionType": "git"}, {"status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "3d3abf3f7e8b1abb082070a343de82d7efc80523", "versionType": "git"}, {"status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "e7177c7e32cb806f348387b7f4faafd4a5b32054", "versionType": "git"}, {"status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "3a062a5c55adc5507600b9ae6d911e247e2f1d6e", "versionType": "git"}, {"status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "7366830642505683bbe905a2ba5d18d6e4b512b8", "versionType": "git"}, {"status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "lessThan": "e750f85391286a4c8100275516973324b621a269", "versionType": "git"}], "programFiles": ["arch/x86/kvm/emulate.c", "arch/x86/kvm/kvm_emulate.h", "arch/x86/kvm/x86.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "3.0"}, {"status": "unaffected", "version": "0", "lessThan": "3.0", "versionType": "semver"}, {"status": "unaffected", "version": "5.4.301", "versionType": "semver", "lessThanOrEqual": "5.4.*"}, {"status": "unaffected", "version": "5.10.246", "versionType": "semver", "lessThanOrEqual": "5.10.*"}, {"status": "unaffected", "version": "5.15.195", "versionType": "semver", "lessThanOrEqual": "5.15.*"}, {"status": "unaffected", "version": "6.1.157", "versionType": "semver", "lessThanOrEqual": "6.1.*"}, {"status": "unaffected", "version": "6.6.111", "versionType": "semver", "lessThanOrEqual": "6.6.*"}, {"status": "unaffected", "version": "6.12.52", "versionType": "semver", "lessThanOrEqual": "6.12.*"}, {"status": "unaffected", "version": "6.16.12", "versionType": "semver", "lessThanOrEqual": "6.16.*"}, {"status": "unaffected", "version": "6.17.2", "versionType": "semver", "lessThanOrEqual": "6.17.*"}, {"status": "unaffected", "version": "6.18", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["arch/x86/kvm/emulate.c", "arch/x86/kvm/kvm_emulate.h", "arch/x86/kvm/x86.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/a908eca437789589dd4624da428614c1275064dc"}, {"url": "https://git.kernel.org/stable/c/00338255bb1f422642fb2798ebe92e93b6e4209b"}, {"url": "https://git.kernel.org/stable/c/e0ce3ed1048a47986d15aef1a98ebda25560d257"}, {"url": "https://git.kernel.org/stable/c/ba35a5d775799ce5ad60230be97336f2fefd518e"}, {"url": "https://git.kernel.org/stable/c/3d3abf3f7e8b1abb082070a343de82d7efc80523"}, {"url": "https://git.kernel.org/stable/c/e7177c7e32cb806f348387b7f4faafd4a5b32054"}, {"url": "https://git.kernel.org/stable/c/3a062a5c55adc5507600b9ae6d911e247e2f1d6e"}, {"url": "https://git.kernel.org/stable/c/7366830642505683bbe905a2ba5d18d6e4b512b8"}, {"url": "https://git.kernel.org/stable/c/e750f85391286a4c8100275516973324b621a269"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Don't (re)check L1 intercepts when completing userspace I/O\n\nWhen completing emulation of instruction that generated a userspace exit\nfor I/O, don't recheck L1 intercepts as KVM has already finished that\nphase of instruction execution, i.e. has already committed to allowing L2\nto perform I/O. If L1 (or host userspace) modifies the I/O permission\nbitmaps during the exit to userspace, KVM will treat the access as being\nintercepted despite already having emulated the I/O access.\n\nPivot on EMULTYPE_NO_DECODE to detect that KVM is completing emulation.\nOf the three users of EMULTYPE_NO_DECODE, only complete_emulated_io() (the\nintended \"recipient\") can reach the code in question. gp_interception()'s\nuse is mutually exclusive with is_guest_mode(), and\ncomplete_emulated_insn_gp() unconditionally pairs EMULTYPE_NO_DECODE with\nEMULTYPE_SKIP.\n\nThe bad behavior was detected by a syzkaller program that toggles port I/O\ninterception during the userspace I/O exit, ultimately resulting in a WARN\non vcpu->arch.pio.count being non-zero due to KVM no completing emulation\nof the I/O instruction.\n\n WARNING: CPU: 23 PID: 1083 at arch/x86/kvm/x86.c:8039 emulator_pio_in_out+0x154/0x170 [kvm]\n Modules linked in: kvm_intel kvm irqbypass\n CPU: 23 UID: 1000 PID: 1083 Comm: repro Not tainted 6.16.0-rc5-c1610d2d66b1-next-vm #74 NONE\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n RIP: 0010:emulator_pio_in_out+0x154/0x170 [kvm]\n PKRU: 55555554\n Call Trace:\n <TASK>\n kvm_fast_pio+0xd6/0x1d0 [kvm]\n vmx_handle_exit+0x149/0x610 [kvm_intel]\n kvm_arch_vcpu_ioctl_run+0xda8/0x1ac0 [kvm]\n kvm_vcpu_ioctl+0x244/0x8c0 [kvm]\n __x64_sys_ioctl+0x8a/0xd0\n do_syscall_64+0x5d/0xc60\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n </TASK>"}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.4.301", "versionStartIncluding": "3.0"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.246", "versionStartIncluding": "3.0"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.195", "versionStartIncluding": "3.0"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.157", "versionStartIncluding": "3.0"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.111", "versionStartIncluding": "3.0"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.52", "versionStartIncluding": "3.0"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.16.12", "versionStartIncluding": "3.0"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.17.2", "versionStartIncluding": "3.0"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.18", "versionStartIncluding": "3.0"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:07:08.793Z"}}}, "cveMetadata": {"cveId": "CVE-2025-40026", "state": "PUBLISHED", "dateUpdated": "2026-10-15T22:02:36.361Z", "dateReserved": "2025-04-16T07:20:57.152Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2025-10-28T09:32:33.075Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["arch/x86/kvm/emulate.c", "arch/x86/kvm/kvm_emulate.h", "arch/x86/kvm/x86.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "a908eca437789589dd4624da428614c1275064dc", "status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "versionType": "git"}, {"lessThan": "00338255bb1f422642fb2798ebe92e93b6e4209b", "status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "versionType": "git"}, {"lessThan": "e0ce3ed1048a47986d15aef1a98ebda25560d257", "status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "versionType": "git"}, {"lessThan": "ba35a5d775799ce5ad60230be97336f2fefd518e", "status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "versionType": "git"}, {"lessThan": "3d3abf3f7e8b1abb082070a343de82d7efc80523", "status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "versionType": "git"}, {"lessThan": "e7177c7e32cb806f348387b7f4faafd4a5b32054", "status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "versionType": "git"}, {"lessThan": "3a062a5c55adc5507600b9ae6d911e247e2f1d6e", "status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "versionType": "git"}, {"lessThan": "7366830642505683bbe905a2ba5d18d6e4b512b8", "status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "versionType": "git"}, {"lessThan": "e750f85391286a4c8100275516973324b621a269", "status": "affected", "version": "8a76d7f25f8f24fc5a328c8e15e4a7313cf141b9", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["arch/x86/kvm/emulate.c", "arch/x86/kvm/kvm_emulate.h", "arch/x86/kvm/x86.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "3.0"}, {"lessThan": "3.0", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "5.4.*", "status": "unaffected", "version": "5.4.301", "versionType": "semver"}, {"lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.246", "versionType": "semver"}, {"lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.195", "versionType": "semver"}, {"lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.157", "versionType": "semver"}, {"lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.111", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.52", "versionType": "semver"}, {"lessThanOrEqual": "6.16.*", "status": "unaffected", "version": "6.16.12", "versionType": "semver"}, {"lessThanOrEqual": "6.17.*", "status": "unaffected", "version": "6.17.2", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "6.18", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Don't (re)check L1 intercepts when completing userspace I/O\n\nWhen completing emulation of instruction that generated a userspace exit\nfor I/O, don't recheck L1 intercepts as KVM has already finished that\nphase of instruction execution, i.e. has already committed to allowing L2\nto perform I/O. If L1 (or host userspace) modifies the I/O permission\nbitmaps during the exit to userspace, KVM will treat the access as being\nintercepted despite already having emulated the I/O access.\n\nPivot on EMULTYPE_NO_DECODE to detect that KVM is completing emulation.\nOf the three users of EMULTYPE_NO_DECODE, only complete_emulated_io() (the\nintended \"recipient\") can reach the code in question. gp_interception()'s\nuse is mutually exclusive with is_guest_mode(), and\ncomplete_emulated_insn_gp() unconditionally pairs EMULTYPE_NO_DECODE with\nEMULTYPE_SKIP.\n\nThe bad behavior was detected by a syzkaller program that toggles port I/O\ninterception during the userspace I/O exit, ultimately resulting in a WARN\non vcpu->arch.pio.count being non-zero due to KVM no completing emulation\nof the I/O instruction.\n\n WARNING: CPU: 23 PID: 1083 at arch/x86/kvm/x86.c:8039 emulator_pio_in_out+0x154/0x170 [kvm]\n Modules linked in: kvm_intel kvm irqbypass\n CPU: 23 UID: 1000 PID: 1083 Comm: repro Not tainted 6.16.0-rc5-c1610d2d66b1-next-vm #74 NONE\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n RIP: 0010:emulator_pio_in_out+0x154/0x170 [kvm]\n PKRU: 55555554\n Call Trace:\n <TASK>\n kvm_fast_pio+0xd6/0x1d0 [kvm]\n vmx_handle_exit+0x149/0x610 [kvm_intel]\n kvm_arch_vcpu_ioctl_run+0xda8/0x1ac0 [kvm]\n kvm_vcpu_ioctl+0x244/0x8c0 [kvm]\n __x64_sys_ioctl+0x8a/0xd0\n do_syscall_64+0x5d/0xc60\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n </TASK>"}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nKVM: x86: No (re)verificar las intercepciones L1 al completar la E/S del espacio de usuario\n\nAl completar la emulaci\u00f3n de una instrucci\u00f3n que gener\u00f3 una salida al espacio de usuario para E/S, no volver a verificar las intercepciones L1 ya que KVM ya ha terminado esa fase de ejecuci\u00f3n de la instrucci\u00f3n, es decir, ya se ha comprometido a permitir que L2 realice E/S. Si L1 (o el espacio de usuario del host) modifica los mapas de bits de permisos de E/S durante la salida al espacio de usuario, KVM tratar\u00e1 el acceso como interceptado a pesar de haber emulado ya el acceso de E/S.\n\nBasarse en EMULTYPE_NO_DECODE para detectar que KVM est\u00e1 completando la emulaci\u00f3n. De los tres usuarios de EMULTYPE_NO_DECODE, solo complete_emulated_io() (el 'destinatario' previsto) puede alcanzar el c\u00f3digo en cuesti\u00f3n. El uso de gp_interception() es mutuamente excluyente con is_guest_mode(), y complete_emulated_insn_gp() empareja incondicionalmente EMULTYPE_NO_DECODE con EMULTYPE_SKIP.\n\nEl comportamiento err\u00f3neo fue detectado por un programa syzkaller que alterna la intercepci\u00f3n de E/S del puerto durante la salida de E/S del espacio de usuario, lo que finalmente result\u00f3 en una ADVERTENCIA (WARN) sobre vcpu->arch.pio.count siendo distinto de cero debido a que KVM no complet\u00f3 la emulaci\u00f3n de la instrucci\u00f3n de E/S.\n\n ADVERTENCIA: CPU: 23 PID: 1083 en arch/x86/kvm/x86.c:8039 emulator_pio_in_out+0x154/0x170 [kvm]\n M\u00f3dulos enlazados: kvm_intel kvm irqbypass\n CPU: 23 UID: 1000 PID: 1083 Comm: repro No contaminado 6.16.0-rc5-c1610d2d66b1-next-vm #74 NINGUNO\n Nombre del hardware: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n RIP: 0010:emulator_pio_in_out+0x154/0x170 [kvm]\n PKRU: 55555554\n Traza de llamada:\n <TAREA>\n kvm_fast_pio+0xd6/0x1d0 [kvm]\n vmx_handle_exit+0x149/0x610 [kvm_intel]\n kvm_arch_vcpu_ioctl_run+0xda8/0x1ac0 [kvm]\n kvm_vcpu_ioctl+0x244/0x8c0 [kvm]\n __x64_sys_ioctl+0x8a/0xd0\n do_syscall_64+0x5d/0xc60\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n </TAREA>"}], "id": "CVE-2025-40026", "lastModified": "2026-10-19T21:10:00.160", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.9, "baseSeverity": "HIGH", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "CHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H", "version": "3.1"}, "exploitabilityScore": 2.0, "impactScore": 5.3, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2025-40026", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-10-15T21:56:14.274469Z", "version": "2.0.3"}}]}, "published": "2025-10-28T10:15:42.167", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/00338255bb1f422642fb2798ebe92e93b6e4209b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/3a062a5c55adc5507600b9ae6d911e247e2f1d6e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/3d3abf3f7e8b1abb082070a343de82d7efc80523"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/7366830642505683bbe905a2ba5d18d6e4b512b8"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/a908eca437789589dd4624da428614c1275064dc"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/ba35a5d775799ce5ad60230be97336f2fefd518e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/e0ce3ed1048a47986d15aef1a98ebda25560d257"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/e7177c7e32cb806f348387b7f4faafd4a5b32054"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/e750f85391286a4c8100275516973324b621a269"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Deferred"}

{"bugzilla": {"description": "kernel: KVM: x86: Don't (re)check L1 intercepts when completing userspace I/O", "id": "2406712", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2406712"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "details": ["No description is available for this CVE."], "name": "CVE-2025-40026", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2025-10-28T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-40026\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-40026\nhttps://lore.kernel.org/linux-cve-announce/2025102841-CVE-2025-40026-760b@gregkh/T"], "threat_severity": "Moderate"}

{"created": "2025-10-29T10:58:46.658106+00:00", "updated": "2025-10-29T10:58:46.658131+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}