CVE-2026-23086

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A malicious guest can advertise\na large buffer and read slowly, causing the host to allocate a\ncorrespondingly large amount of sk_buff memory.\nThe same thing would happen in the guest with a malicious host, since\nvirtio transports share the same code base.\n\nIntroduce a small helper, virtio_transport_tx_buf_size(), that\nreturns min(peer_buf_alloc, buf_alloc), and use it wherever we consume\npeer_buf_alloc.\n\nThis ensures the effective TX window is bounded by both the peer's\nadvertised buffer and our own buf_alloc (already clamped to\nbuffer_max_size via SO_VM_SOCKETS_BUFFER_MAX_SIZE), so a remote peer\ncannot force the other to queue more data than allowed by its own\nvsock settings.\n\nOn an unpatched Ubuntu 22.04 host (~64 GiB RAM), running a PoC with\n32 guest vsock connections advertising 2 GiB each and reading slowly\ndrove Slab/SUnreclaim from ~0.5 GiB to ~57 GiB; the system only\nrecovered after killing the QEMU process. That said, if QEMU memory is\nlimited with cgroups, the maximum memory used will be limited.\n\nWith this patch applied:\n\n Before:\n MemFree: ~61.6 GiB\n Slab: ~142 MiB\n SUnreclaim: ~117 MiB\n\n After 32 high-credit connections:\n MemFree: ~61.5 GiB\n Slab: ~178 MiB\n SUnreclaim: ~152 MiB\n\nOnly ~35 MiB increase in Slab/SUnreclaim, no host OOM, and the guest\nremains responsive.\n\nCompatibility with non-virtio transports:\n\n - VMCI uses the AF_VSOCK buffer knobs to size its queue pairs per\n socket based on the local vsk->buffer_* values; the remote side\n cannot enlarge those queues beyond what the local endpoint\n configured.\n\n - Hyper-V's vsock transport uses fixed-size VMBus ring buffers and\n an MTU bound; there is no peer-controlled credit field comparable\n to peer_buf_alloc, and the remote endpoint cannot drive in-flight\n kernel memory above those ring sizes.\n\n - The loopback path reuses virtio_transport_common.c, so it\n naturally follows the same semantics as the virtio transport.\n\nThis change is limited to virtio_transport_common.c and thus affects\nvirtio-vsock, vhost-vsock, and loopback, bringing them in line with the\n\"remote window intersected with local policy\" behaviour that VMCI and\nHyper-V already effectively have.\n\n[Stefano: small adjustments after changing the previous patch]\n[Stefano: tweak the commit message]"}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/vmw_vsock/virtio_transport_common.c"], "versions": [{"version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "lessThan": "fef7110ae5617555c792a2bb4d27878d84583adf", "status": "affected", "versionType": "git"}, {"version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "lessThan": "d9d5f222558b42f6277eafaaa6080966faf37676", "status": "affected", "versionType": "git"}, {"version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "lessThan": "c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce", "status": "affected", "versionType": "git"}, {"version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "lessThan": "84ef86aa7120449828d1e0ce438c499014839711", "status": "affected", "versionType": "git"}, {"version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "lessThan": "8ee784fdf006cbe8739cfa093f54d326cbf54037", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["net/vmw_vsock/virtio_transport_common.c"], "versions": [{"version": "4.8", "status": "affected"}, {"version": "0", "lessThan": "4.8", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.162", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.122", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.68", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.8", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19", "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": "4.8", "versionEndExcluding": "6.1.162"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.6.122"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.12.68"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.18.8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.19"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/fef7110ae5617555c792a2bb4d27878d84583adf"}, {"url": "https://git.kernel.org/stable/c/d9d5f222558b42f6277eafaaa6080966faf37676"}, {"url": "https://git.kernel.org/stable/c/c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce"}, {"url": "https://git.kernel.org/stable/c/84ef86aa7120449828d1e0ce438c499014839711"}, {"url": "https://git.kernel.org/stable/c/8ee784fdf006cbe8739cfa093f54d326cbf54037"}], "title": "vsock/virtio: cap TX credit to local buffer size", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-23086", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-06-10T20:42:20.829487Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-400", "description": "CWE-400 Uncontrolled Resource Consumption"}]}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-19T18:25:30.062Z"}}, {"x_adpType": "supplier", "providerMetadata": {"orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "shortName": "siemens-SADP", "dateUpdated": "2026-11-10T12:41:37.802Z"}, "affected": [{"vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)", "versions": [{"status": "affected", "version": "V3.1.6", "lessThan": "*", "versionType": "custom"}], "defaultStatus": "unknown"}, {"vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)", "versions": [{"status": "affected", "version": "V3.1.7", "lessThan": "*", "versionType": "custom"}], "defaultStatus": "unknown"}, {"vendor": "Siemens", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)", "versions": 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"134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-06-11T17:39:18.915Z"}}], "cna": {"title": "vsock/virtio: cap TX credit to local buffer size", "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "lessThan": "fef7110ae5617555c792a2bb4d27878d84583adf", "versionType": "git"}, {"status": "affected", "version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "lessThan": "d9d5f222558b42f6277eafaaa6080966faf37676", "versionType": "git"}, {"status": "affected", "version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "lessThan": "c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce", "versionType": "git"}, {"status": "affected", "version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "lessThan": "84ef86aa7120449828d1e0ce438c499014839711", "versionType": "git"}, {"status": "affected", "version": 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"programFiles": ["net/vmw_vsock/virtio_transport_common.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/fef7110ae5617555c792a2bb4d27878d84583adf"}, {"url": "https://git.kernel.org/stable/c/d9d5f222558b42f6277eafaaa6080966faf37676"}, {"url": "https://git.kernel.org/stable/c/c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce"}, {"url": "https://git.kernel.org/stable/c/84ef86aa7120449828d1e0ce438c499014839711"}, {"url": "https://git.kernel.org/stable/c/8ee784fdf006cbe8739cfa093f54d326cbf54037"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvsock/virtio: cap TX credit to local buffer size\n\nThe virtio transports derives its TX credit directly from peer_buf_alloc,\nwhich is set from the remote endpoint's SO_VM_SOCKETS_BUFFER_SIZE value.\n\nOn the host side this means that the amount of data we are willing to\nqueue for a connection is scaled by a guest-chosen buffer size, rather\nthan the host's own vsock configuration. A malicious guest can advertise\na large buffer and read slowly, causing the host to allocate a\ncorrespondingly large amount of sk_buff memory.\nThe same thing would happen in the guest with a malicious host, since\nvirtio transports share the same code base.\n\nIntroduce a small helper, virtio_transport_tx_buf_size(), that\nreturns min(peer_buf_alloc, buf_alloc), and use it wherever we consume\npeer_buf_alloc.\n\nThis ensures the effective TX window is bounded by both the peer's\nadvertised buffer and our own buf_alloc (already clamped to\nbuffer_max_size via SO_VM_SOCKETS_BUFFER_MAX_SIZE), so a remote peer\ncannot force the other to queue more data than allowed by its own\nvsock settings.\n\nOn an unpatched Ubuntu 22.04 host (~64 GiB RAM), running a PoC with\n32 guest vsock connections advertising 2 GiB each and reading slowly\ndrove Slab/SUnreclaim from ~0.5 GiB to ~57 GiB; the system only\nrecovered after killing the QEMU process. That said, if QEMU memory is\nlimited with cgroups, the maximum memory used will be limited.\n\nWith this patch applied:\n\n Before:\n MemFree: ~61.6 GiB\n Slab: ~142 MiB\n SUnreclaim: ~117 MiB\n\n After 32 high-credit connections:\n MemFree: ~61.5 GiB\n Slab: ~178 MiB\n SUnreclaim: ~152 MiB\n\nOnly ~35 MiB increase in Slab/SUnreclaim, no host OOM, and the guest\nremains responsive.\n\nCompatibility with non-virtio transports:\n\n - VMCI uses the AF_VSOCK buffer knobs to size its queue pairs per\n socket based on the local vsk->buffer_* values; the remote side\n cannot enlarge those queues beyond what the local endpoint\n configured.\n\n - Hyper-V's vsock transport uses fixed-size VMBus ring buffers and\n an MTU bound; there is no peer-controlled credit field comparable\n to peer_buf_alloc, and the remote endpoint cannot drive in-flight\n kernel memory above those ring sizes.\n\n - The loopback path reuses virtio_transport_common.c, so it\n naturally follows the same semantics as the virtio transport.\n\nThis change is limited to virtio_transport_common.c and thus affects\nvirtio-vsock, vhost-vsock, and loopback, bringing them in line with the\n\"remote window intersected with local policy\" behaviour that VMCI and\nHyper-V already effectively have.\n\n[Stefano: small adjustments after changing the previous patch]\n[Stefano: tweak the commit message]"}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.162", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.122", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.68", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.18.8", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.19", "versionStartIncluding": "4.8"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T21:59:43.793Z"}}}, "cveMetadata": {"cveId": "CVE-2026-23086", "state": "PUBLISHED", "dateUpdated": "2026-11-10T12:41:37.802Z", "dateReserved": "2026-01-13T15:37:45.961Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2026-02-04T16:08:10.047Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["net/vmw_vsock/virtio_transport_common.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "fef7110ae5617555c792a2bb4d27878d84583adf", "status": "affected", "version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "versionType": "git"}, {"lessThan": "d9d5f222558b42f6277eafaaa6080966faf37676", "status": "affected", "version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "versionType": "git"}, {"lessThan": "c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce", "status": "affected", "version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "versionType": "git"}, {"lessThan": "84ef86aa7120449828d1e0ce438c499014839711", "status": "affected", "version": "06a8fc78367d070720af960dcecec917d3ae5f3b", "versionType": "git"}, {"lessThan": "8ee784fdf006cbe8739cfa093f54d326cbf54037", "status": "affected", "version": 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{"affectedData": [{"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.6", "versionType": "custom"}]}, {"defaultStatus": "unknown", "product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)", "vendor": "Siemens", "versions": [{"lessThan": "*", "status": "affected", "version": "V3.1.7", "versionType": "custom"}]}], "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "68145F3E-ECEF-4C5B-95B5-996FCDAD1705", "versionEndExcluding": "6.1.162", "versionStartIncluding": "4.8", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "8EAAE395-0162-4BAF-9AD5-E9AF3C869C4F", "versionEndExcluding": "6.6.122", "versionStartIncluding": "6.2", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "52F38E19-0FDD-4992-9D6D-D4169D689598", "versionEndExcluding": "6.12.68", "versionStartIncluding": "6.7", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "E65C6E79-7EBE-4C77-93F0-818CF5B38F4E", "versionEndExcluding": "6.18.8", "versionStartIncluding": "6.13", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.19:rc1:*:*:*:*:*:*", "matchCriteriaId": "17B67AA7-40D6-4AFA-8459-F200F3D7CFD1", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.19:rc2:*:*:*:*:*:*", "matchCriteriaId": "C47E4CC9-C826-4FA9-B014-7FE3D9B318B2", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.19:rc3:*:*:*:*:*:*", "matchCriteriaId": "F71D92C0-C023-48BD-B3B6-70B638EEE298", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.19:rc4:*:*:*:*:*:*", "matchCriteriaId": "13580667-0A98-40CC-B29F-D12790B91BDB", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.19:rc5:*:*:*:*:*:*", "matchCriteriaId": "CAD1FED7-CF48-47BF-AC7D-7B6FA3C065FC", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.19:rc6:*:*:*:*:*:*", "matchCriteriaId": "3EF854A1-ABB1-4E93-BE9A-44569EC76C0D", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nvsock/virtio: cap TX credit to local buffer size\n\nThe virtio transports derives its TX credit directly from peer_buf_alloc,\nwhich is set from the remote endpoint's SO_VM_SOCKETS_BUFFER_SIZE value.\n\nOn the host side this means that the amount of data we are willing to\nqueue for a connection is scaled by a guest-chosen buffer size, rather\nthan the host's own vsock configuration. A malicious guest can advertise\na large buffer and read slowly, causing the host to allocate a\ncorrespondingly large amount of sk_buff memory.\nThe same thing would happen in the guest with a malicious host, since\nvirtio transports share the same code base.\n\nIntroduce a small helper, virtio_transport_tx_buf_size(), that\nreturns min(peer_buf_alloc, buf_alloc), and use it wherever we consume\npeer_buf_alloc.\n\nThis ensures the effective TX window is bounded by both the peer's\nadvertised buffer and our own buf_alloc (already clamped to\nbuffer_max_size via SO_VM_SOCKETS_BUFFER_MAX_SIZE), so a remote peer\ncannot force the other to queue more data than allowed by its own\nvsock settings.\n\nOn an unpatched Ubuntu 22.04 host (~64 GiB RAM), running a PoC with\n32 guest vsock connections advertising 2 GiB each and reading slowly\ndrove Slab/SUnreclaim from ~0.5 GiB to ~57 GiB; the system only\nrecovered after killing the QEMU process. That said, if QEMU memory is\nlimited with cgroups, the maximum memory used will be limited.\n\nWith this patch applied:\n\n Before:\n MemFree: ~61.6 GiB\n Slab: ~142 MiB\n SUnreclaim: ~117 MiB\n\n After 32 high-credit connections:\n MemFree: ~61.5 GiB\n Slab: ~178 MiB\n SUnreclaim: ~152 MiB\n\nOnly ~35 MiB increase in Slab/SUnreclaim, no host OOM, and the guest\nremains responsive.\n\nCompatibility with non-virtio transports:\n\n - VMCI uses the AF_VSOCK buffer knobs to size its queue pairs per\n socket based on the local vsk->buffer_* values; the remote side\n cannot enlarge those queues beyond what the local endpoint\n configured.\n\n - Hyper-V's vsock transport uses fixed-size VMBus ring buffers and\n an MTU bound; there is no peer-controlled credit field comparable\n to peer_buf_alloc, and the remote endpoint cannot drive in-flight\n kernel memory above those ring sizes.\n\n - The loopback path reuses virtio_transport_common.c, so it\n naturally follows the same semantics as the virtio transport.\n\nThis change is limited to virtio_transport_common.c and thus affects\nvirtio-vsock, vhost-vsock, and loopback, bringing them in line with the\n\"remote window intersected with local policy\" behaviour that VMCI and\nHyper-V already effectively have.\n\n[Stefano: small adjustments after changing the previous patch]\n[Stefano: tweak the commit message]"}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nvsock/virtio: limitar el cr\u00e9dito TX al tama\u00f1o del b\u00fafer local\n\nLos transportes virtio derivan su cr\u00e9dito TX directamente de peer_buf_alloc, que se establece a partir del valor SO_VM_SOCKETS_BUFFER_SIZE del punto final remoto.\n\nEn el lado del host, esto significa que la cantidad de datos que estamos dispuestos a encolar para una conexi\u00f3n se escala por un tama\u00f1o de b\u00fafer elegido por el invitado, en lugar de la propia configuraci\u00f3n vsock del host. Un invitado malicioso puede anunciar un b\u00fafer grande y leer lentamente, haciendo que el host asigne una cantidad correspondientemente grande de memoria sk_buff.\nLo mismo ocurrir\u00eda en el invitado con un host malicioso, ya que los transportes virtio comparten la misma base de c\u00f3digo.\n\nIntroducir una peque\u00f1a funci\u00f3n auxiliar, virtio_transport_tx_buf_size(), que devuelve min(peer_buf_alloc, buf_alloc), y usarla dondequiera que consumamos peer_buf_alloc.\n\nEsto asegura que la ventana TX efectiva est\u00e9 limitada tanto por el b\u00fafer anunciado del par como por nuestro propio buf_alloc (ya ajustado a buffer_max_size a trav\u00e9s de SO_VM_SOCKETS_BUFFER_MAX_SIZE), de modo que un par remoto no pueda forzar al otro a encolar m\u00e1s datos de los permitidos por su propia configuraci\u00f3n vsock.\n\nEn un host Ubuntu 22.04 sin parchear (~64 GiB de RAM), ejecutar una PoC con 32 conexiones vsock de invitado anunciando 2 GiB cada una y leyendo lentamente llev\u00f3 Slab/SUnreclaim de ~0.5 GiB a ~57 GiB; el sistema solo se recuper\u00f3 despu\u00e9s de terminar el proceso QEMU. Dicho esto, si la memoria de QEMU est\u00e1 limitada con cgroups, la memoria m\u00e1xima utilizada estar\u00e1 limitada.\n\nCon este parche aplicado:\n\n Antes:\n MemFree: ~61.6 GiB\n Slab: ~142 MiB\n SUnreclaim: ~117 MiB\n\n Despu\u00e9s de 32 conexiones de alto cr\u00e9dito:\n MemFree: ~61.5 GiB\n Slab: ~178 MiB\n SUnreclaim: ~152 MiB\n\nSolo un aumento de ~35 MiB en Slab/SUnreclaim, sin OOM del host, y el invitado permanece receptivo.\n\nCompatibilidad con transportes no virtio:\n\n - VMCI utiliza los controles de b\u00fafer AF_VSOCK para dimensionar sus pares de cola por socket bas\u00e1ndose en los valores locales vsk->buffer_*; el lado remoto no puede ampliar esas colas m\u00e1s all\u00e1 de lo que configur\u00f3 el punto final local.\n\n - El transporte vsock de Hyper-V utiliza b\u00faferes de anillo VMBus de tama\u00f1o fijo y un l\u00edmite de MTU; no hay un campo de cr\u00e9dito controlado por el par comparable a peer_buf_alloc, y el punto final remoto no puede impulsar la memoria del kernel en tr\u00e1nsito por encima de esos tama\u00f1os de anillo.\n\n - La ruta de bucle invertido reutiliza virtio_transport_common.c, por lo que naturalmente sigue la misma sem\u00e1ntica que el transporte virtio.\n\nEste cambio se limita a virtio_transport_common.c y por lo tanto afecta a virtio-vsock, vhost-vsock y loopback, poni\u00e9ndolos en l\u00ednea con el comportamiento de 'ventana remota intersectada con pol\u00edtica local' que VMCI y Hyper-V ya tienen efectivamente.\n\n[Stefano: peque\u00f1os ajustes despu\u00e9s de cambiar el parche anterior]\n[Stefano: ajustar el mensaje de commit]"}], "id": "CVE-2026-23086", "lastModified": "2026-11-10T13:18:34.407", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "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:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-23086", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-06-10T20:42:20.829487Z", "version": "2.0.3"}}]}, "published": "2026-02-04T17:16:19.467", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/84ef86aa7120449828d1e0ce438c499014839711"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/8ee784fdf006cbe8739cfa093f54d326cbf54037"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c0e42fb0e054c2b2ec4ee80f48ccd256ae0227ce"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d9d5f222558b42f6277eafaaa6080966faf37676"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/fef7110ae5617555c792a2bb4d27878d84583adf"}, {"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"}, {"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "url": "https://cert-portal.siemens.com/productcert/html/ssa-457936.html"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}, {"description": [{"lang": "en", "value": "CWE-400"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "kernel: vsock/virtio: cap TX credit to local buffer size", "id": "2436799", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2436799"}, "csaw": false, "cvss3": {"cvss3_base_score": "6.2", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "details": ["No description is available for this CVE."], "mitigation": {"lang": "en:us", "value": "To mitigate this issue, prevent module vsock from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically."}, "name": "CVE-2026-23086", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "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": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-02-04T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-23086\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-23086\nhttps://lore.kernel.org/linux-cve-announce/2026020423-CVE-2026-23086-9ad9@gregkh/T"], "statement": "The bug is in the Virtual Socket Protocol (that is a socket protocol similar to TCP/IP allowing communication between Virtual Machines and hypervisor or host). A memory exhaustion denial of service can be triggered in virtio vsock because the transmit credit was derived directly from the peer advertised peer_buf_alloc value. A malicious peer can advertise a very large receive buffer and then read slowly. This causes the other endpoint to queue far more sk_buff data than its local vsock policy intended and can drive slab usage to extreme levels leading to OOM and service disruption. For the CVSS the PR is N because an unprivileged process that can open an AF_VSOCK connection can influence SO_VM_SOCKETS_BUFFER_SIZE on its endpoint. The issue is reachable across the vsock channel which often crosses VM boundaries between a guest and a host even though it is not a traditional IP network. Impact is denial of service through memory pressure and potential process termination such as killing QEMU on the host.", "threat_severity": "Moderate"}

{"analysis": {"en": {"generated_at": "2026-04-17T23:35:23.659443+00:00", "value": {"mitigation_remediation": ["Upgrade the Linux kernel to a release that includes the virtio_transport_tx_buf_size patch (such as kernel 6.19 rc6 or later).", "If an immediate kernel upgrade is not feasible, limit the maximum vsock buffer that a guest or host can advertise by configuring SO_VM_SOCKETS_BUFFER_MAX_SIZE or applying cgroup memory constraints to prevent excessive slab allocation.", "Reduce the number of simultaneous virtio\u2011vsock connections or enforce per\u2011VM or per\u2011guest connection limits through hypervisor configuration to mitigate large\u2011buffer amplification.", "Monitor slab allocation and memory usage metrics to detect abnormal growth patterns indicative of exploitation attempts."], "summary": {"action": "Patch immediately", "impact": "Denial of Service via memory exhaustion"}, "threat_synthesis": {"affected_systems": "All Linux kernel builds that include virtio vsock support, such as typical KVM/QEMU hosts and their guests, are affected by this issue in versions before the patch that caps the TX credit to the lower of the peer\u2019s buffer and the local limit. Kernel releases that integrate the virtio_transport_tx_buf_size change, including 6.19 rc6 and later, have removed the flaw.", "description_and_impact": "The vulnerability in the Linux kernel\u2019s virtio vsock transport lets a malicious peer advertise an arbitrarily large send buffer size. This forces the host or guest to reserve an equivalent amount of sk_buff memory, causing slab allocation to grow uncontrollably. An attacker can therefore exhaust kernel memory and trigger out\u2011of\u2011memory conditions or make the system unresponsive. The flaw is a classic case of uncontrolled resource consumption.", "risk_and_exploitability": "The CVSS base score of 5.5 indicates moderate severity, while an EPSS value of less than 1% points to a low likelihood of exploitation. The vulnerability is not listed in the CISA KEV catalog. Exploitation requires control over a virtual machine or host to open many vsock connections advertising large buffers; such activity can be detected and limited with cgroups or memory constraints. Successful exploitation can consume tens of gigabytes of memory, potentially leading to kernel OOM kills and downtime."}}}}, "created": "2026-04-17T23:45:25.809462+00:00", "updated": "2026-04-17T23:45:25.809473+00:00", "vendors": [], "weaknesses": ["CWE-400"]}