CVE-2025-21851

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If this address is not page-aligned\nthe code ends up calling apply_to_pte_range() with that unaligned\naddress causing soft lockup.\n\nFix it by round up GUARD_SZ to PAGE_SIZE << 1 so that the\ndivision by 2 in bpf_arena_get_kern_vm_start() returns\na page-aligned value."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - The vulnerability is reached through the bpf(2) syscall \u2014 creating a BPF_MAP_TYPE_ARENA map, mmap()ing it, faulting in a page, and closing the fd. No network exposure is involved.\nAC:L - On an affected kernel (arm64 with 64K pages, a mainstream aarch64 distro/server configuration), the unaligned base address makes the non-terminating apply_to_pte_range() loop trigger 100% deterministically with a trivial 4-step sequence; there is no race or memory-layout condition to win.\nPR:L - Arena map creation requires CAP_BPF, but bpf_token_capable() resolves via ns_capable(token->userns, CAP_BPF), so a delegated BPF token or a container granted CAP_BPF lets an otherwise unprivileged user reach it; this is a delegatable capability, not init-namespace root.\nUI:N - The attacker performs the entire sequence \u2014 map create, mmap, page touch, fd close \u2014 in their own process. No victim action is required.\nS:U - The infinite loop, out-of-bounds page-table walk, and page frees all occur within the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Once pte++ walks past the end of the PTE page, arbitrary kernel memory is read and interpreted as page-table entries, and __free_page() on garbage-derived struct pages releases in-use pages for reallocation, which is leverageable for disclosure of other tasks' data.\nI:H - existing_page_cb() calls __free_page() on struct page pointers decoded from out-of-bounds memory, corrupting page refcounts and prematurely freeing live pages \u2014 a use-after-free primitive suitable for heap grooming and control-flow hijacking.\nA:H - The `while (addr += PAGE_SIZE, addr != end)` loop can never terminate, producing a soft lockup/RCU stall inside a lazy-MMU section on a system workqueue, hanging the machine; the stray page frees compound this into a panic."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/bpf/arena.c"], "versions": [{"version": "317460317a02a1af512697e6e964298dedd8a163", "lessThan": "c1f3f3892d4526f18aaeffdb6068ce861e793ee3", "status": "affected", "versionType": "git"}, {"version": "317460317a02a1af512697e6e964298dedd8a163", "lessThan": "787d556a3de447e70964a4bdeba9196f62a62b1e", "status": "affected", "versionType": "git"}, {"version": "317460317a02a1af512697e6e964298dedd8a163", "lessThan": "517e8a7835e8cfb398a0aeb0133de50e31cae32b", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["kernel/bpf/arena.c"], "versions": [{"version": "6.9", "status": "affected"}, {"version": "0", "lessThan": "6.9", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.17", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.13.5", "lessThanOrEqual": "6.13.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.14", "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": "6.9", "versionEndExcluding": "6.12.17"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.13.5"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.14"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/c1f3f3892d4526f18aaeffdb6068ce861e793ee3"}, {"url": "https://git.kernel.org/stable/c/787d556a3de447e70964a4bdeba9196f62a62b1e"}, {"url": "https://git.kernel.org/stable/c/517e8a7835e8cfb398a0aeb0133de50e31cae32b"}], "title": "bpf: Fix softlockup in arena_map_free on 64k page kernel", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 3.3, "attackVector": "LOCAL", "baseSeverity": "LOW", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "LOW", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2025-21851", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2025-10-01T19:26:12.815420Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-667", "description": "CWE-667 Improper Locking"}]}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2025-10-01T19:26:38.747Z"}}]}}

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No network exposure is involved.\nAC:L - On an affected kernel (arm64 with 64K pages, a mainstream aarch64 distro/server configuration), the unaligned base address makes the non-terminating apply_to_pte_range() loop trigger 100% deterministically with a trivial 4-step sequence; there is no race or memory-layout condition to win.\nPR:L - Arena map creation requires CAP_BPF, but bpf_token_capable() resolves via ns_capable(token->userns, CAP_BPF), so a delegated BPF token or a container granted CAP_BPF lets an otherwise unprivileged user reach it; this is a delegatable capability, not init-namespace root.\nUI:N - The attacker performs the entire sequence \u2014 map create, mmap, page touch, fd close \u2014 in their own process. No victim action is required.\nS:U - The infinite loop, out-of-bounds page-table walk, and page frees all occur within the kernel's own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Once pte++ walks past the end of the PTE page, arbitrary kernel memory is read and interpreted as page-table entries, and __free_page() on garbage-derived struct pages releases in-use pages for reallocation, which is leverageable for disclosure of other tasks' data.\nI:H - existing_page_cb() calls __free_page() on struct page pointers decoded from out-of-bounds memory, corrupting page refcounts and prematurely freeing live pages \u2014 a use-after-free primitive suitable for heap grooming and control-flow hijacking.\nA:H - The `while (addr += PAGE_SIZE, addr != end)` loop can never terminate, producing a soft lockup/RCU stall inside a lazy-MMU section on a system workqueue, hanging the machine; the stray page frees compound this into a panic."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "317460317a02a1af512697e6e964298dedd8a163", "lessThan": "c1f3f3892d4526f18aaeffdb6068ce861e793ee3", "versionType": "git"}, {"status": "affected", "version": "317460317a02a1af512697e6e964298dedd8a163", "lessThan": "787d556a3de447e70964a4bdeba9196f62a62b1e", "versionType": "git"}, {"status": "affected", "version": "317460317a02a1af512697e6e964298dedd8a163", "lessThan": "517e8a7835e8cfb398a0aeb0133de50e31cae32b", "versionType": "git"}], "programFiles": ["kernel/bpf/arena.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "6.9"}, {"status": "unaffected", "version": "0", "lessThan": "6.9", "versionType": "semver"}, {"status": "unaffected", "version": "6.12.17", "versionType": "semver", "lessThanOrEqual": "6.12.*"}, {"status": "unaffected", "version": "6.13.5", "versionType": "semver", "lessThanOrEqual": "6.13.*"}, {"status": "unaffected", "version": "6.14", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["kernel/bpf/arena.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/c1f3f3892d4526f18aaeffdb6068ce861e793ee3"}, {"url": "https://git.kernel.org/stable/c/787d556a3de447e70964a4bdeba9196f62a62b1e"}, {"url": "https://git.kernel.org/stable/c/517e8a7835e8cfb398a0aeb0133de50e31cae32b"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix softlockup in arena_map_free on 64k page kernel\n\nOn an aarch64 kernel with CONFIG_PAGE_SIZE_64KB=y,\narena_htab tests cause a segmentation fault and soft lockup.\nThe same failure is not observed with 4k pages on aarch64.\n\nIt turns out arena_map_free() is calling\napply_to_existing_page_range() with the address returned by\nbpf_arena_get_kern_vm_start(). If this address is not page-aligned\nthe code ends up calling apply_to_pte_range() with that unaligned\naddress causing soft lockup.\n\nFix it by round up GUARD_SZ to PAGE_SIZE << 1 so that the\ndivision by 2 in bpf_arena_get_kern_vm_start() returns\na page-aligned value."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.17", "versionStartIncluding": "6.9"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.13.5", "versionStartIncluding": "6.9"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.14", "versionStartIncluding": "6.9"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:54:55.041Z"}}}, "cveMetadata": {"cveId": "CVE-2025-21851", "state": "PUBLISHED", "dateUpdated": "2026-08-05T11:54:55.041Z", "dateReserved": "2024-12-29T08:45:45.779Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2025-03-12T09:42:06.480Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["kernel/bpf/arena.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "c1f3f3892d4526f18aaeffdb6068ce861e793ee3", "status": "affected", "version": "317460317a02a1af512697e6e964298dedd8a163", "versionType": "git"}, {"lessThan": "787d556a3de447e70964a4bdeba9196f62a62b1e", "status": "affected", "version": "317460317a02a1af512697e6e964298dedd8a163", "versionType": "git"}, {"lessThan": "517e8a7835e8cfb398a0aeb0133de50e31cae32b", "status": "affected", "version": "317460317a02a1af512697e6e964298dedd8a163", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["kernel/bpf/arena.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "6.9"}, {"lessThan": "6.9", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.17", "versionType": "semver"}, {"lessThanOrEqual": "6.13.*", "status": "unaffected", "version": "6.13.5", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "6.14", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "3E513C8F-C336-4B36-A14B-ABDBD0C33C40", "versionEndExcluding": "6.12.17", "versionStartIncluding": "6.9", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "72E69ABB-9015-43A6-87E1-5150383CFFD9", "versionEndExcluding": "6.13.5", "versionStartIncluding": "6.13", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.9:-:*:*:*:*:*:*", "matchCriteriaId": "3F2A4A3D-068A-4CF2-A09F-9C7937DDB0A5", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc1:*:*:*:*:*:*", "matchCriteriaId": "186716B6-2B66-4BD0-852E-D48E71C0C85F", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc2:*:*:*:*:*:*", "matchCriteriaId": "0D3E781C-403A-498F-9DA9-ECEE50F41E75", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc3:*:*:*:*:*:*", "matchCriteriaId": "66619FB8-0AAF-4166-B2CF-67B24143261D", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix softlockup in arena_map_free on 64k page kernel\n\nOn an aarch64 kernel with CONFIG_PAGE_SIZE_64KB=y,\narena_htab tests cause a segmentation fault and soft lockup.\nThe same failure is not observed with 4k pages on aarch64.\n\nIt turns out arena_map_free() is calling\napply_to_existing_page_range() with the address returned by\nbpf_arena_get_kern_vm_start(). If this address is not page-aligned\nthe code ends up calling apply_to_pte_range() with that unaligned\naddress causing soft lockup.\n\nFix it by round up GUARD_SZ to PAGE_SIZE << 1 so that the\ndivision by 2 in bpf_arena_get_kern_vm_start() returns\na page-aligned value."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: bpf: Arregla el bloqueo suave en arena_map_free en un kernel de p\u00e1gina de 64k En un kernel aarch64 con CONFIG_PAGE_SIZE_64KB=y, las pruebas arena_htab causan un fallo de segmentaci\u00f3n y un bloqueo suave. No se observa el mismo fallo con p\u00e1ginas de 4k en aarch64. Resulta que arena_map_free() est\u00e1 llamando a apply_to_existing_page_range() con la direcci\u00f3n devuelta por bpf_arena_get_kern_vm_start(). Si esta direcci\u00f3n no est\u00e1 alineada con la p\u00e1gina, el c\u00f3digo termina llamando a apply_to_pte_range() con esa direcci\u00f3n no alineada, lo que causa un bloqueo suave. Arr\u00e9glelo redondeando GUARD_SZ a PAGE_SIZE &lt;&lt; 1 para que la divisi\u00f3n por 2 en bpf_arena_get_kern_vm_start() devuelva un valor alineado con la p\u00e1gina."}], "id": "CVE-2025-21851", "lastModified": "2026-07-30T06:21:41.180", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "LOW", "baseScore": 3.3, "baseSeverity": "LOW", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 1.4, "source": "nvd@nist.gov", "type": "Primary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "LOW", "baseScore": 3.3, "baseSeverity": "LOW", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 1.4, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2025-21851", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2025-10-01T19:26:12.815420Z", "version": "2.0.3"}}]}, "published": "2025-03-12T10:15:17.703", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/517e8a7835e8cfb398a0aeb0133de50e31cae32b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/787d556a3de447e70964a4bdeba9196f62a62b1e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c1f3f3892d4526f18aaeffdb6068ce861e793ee3"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-667"}], "source": "nvd@nist.gov", "type": "Primary"}, {"description": [{"lang": "en", "value": "CWE-667"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "kernel: bpf: Fix softlockup in arena_map_free on 64k page kernel", "id": "2351606", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2351606"}, "csaw": false, "cvss3": {"cvss3_base_score": "2.3", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L", "status": "draft"}, "cwe": "CWE-667", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nbpf: Fix softlockup in arena_map_free on 64k page kernel\nOn an aarch64 kernel with CONFIG_PAGE_SIZE_64KB=y,\narena_htab tests cause a segmentation fault and soft lockup.\nThe same failure is not observed with 4k pages on aarch64.\nIt turns out arena_map_free() is calling\napply_to_existing_page_range() with the address returned by\nbpf_arena_get_kern_vm_start(). If this address is not page-aligned\nthe code ends up calling apply_to_pte_range() with that unaligned\naddress causing soft lockup.\nFix it by round up GUARD_SZ to PAGE_SIZE << 1 so that the\ndivision by 2 in bpf_arena_get_kern_vm_start() returns\na page-aligned value."], "name": "CVE-2025-21851", "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": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not 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": "2025-03-12T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-21851\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-21851\nhttps://lore.kernel.org/linux-cve-announce/2025031213-CVE-2025-21851-87bd@gregkh/T"], "statement": "The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl. This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space.\nFor the Red Hat Enterprise Linux 9 to confirm the current state, inspect the sysctl with the command:\ncat /proc/sys/kernel/unprivileged_bpf_disabled\nThe setting of 1 would mean that unprivileged users can not use eBPF, mitigating the flaw.", "threat_severity": "Low"}

{}