CVE-2026-31495

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The normal TCP option parsing path already clamps to this value,\n but the ctnetlink path accepted 0-255, causing undefined behavior when\n used as a u32 shift count.\n- CTA_FILTER_ORIG_FLAGS/REPLY_FLAGS: use NLA_POLICY_MASK with\n CTA_FILTER_F_ALL, removing the manual mask checks.\n- CTA_EXPECT_FLAGS: use NLA_POLICY_MASK with NF_CT_EXPECT_MASK, adding\n a new mask define grouping all valid expect flags.\n\nExtracted from a broader nf-next patch by Florian Westphal, scoped to\nctnetlink for the fixes tree."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["include/uapi/linux/netfilter/nf_conntrack_common.h", "net/netfilter/nf_conntrack_netlink.c", "net/netfilter/nf_conntrack_proto_tcp.c"], "versions": [{"version": "c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4", "lessThan": "435b576cd2faa75154777868f8cbb73bf71644d3", "status": "affected", "versionType": "git"}, 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"6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.21", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19.11", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0", "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": "2.6.22", "versionEndExcluding": "5.10.253"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.22", "versionEndExcluding": "5.15.203"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.22", "versionEndExcluding": "6.1.168"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", 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"https://git.kernel.org/stable/c/fcec5ce2d73a41668b24e3f18c803541602a59f6"}, {"url": "https://git.kernel.org/stable/c/675c913b940488a84effdeeac5a1cfb657b59804"}, {"url": "https://git.kernel.org/stable/c/c6cb41eaae875501eaaa487b8db6539feb092292"}, {"url": "https://git.kernel.org/stable/c/45c33e79ae705b7af97e3117672b6cd258dd0b1b"}, {"url": "https://git.kernel.org/stable/c/8f15b5071b4548b0aafc03b366eb45c9c6566704"}], "title": "netfilter: ctnetlink: use netlink policy range checks", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"x_adpType": "supplier", "providerMetadata": {"orgId": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e", "shortName": "siemens-SADP", "dateUpdated": "2026-11-10T12:44:37.122Z"}, "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 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The normal TCP option parsing path already clamps to this value,\n but the ctnetlink path accepted 0-255, causing undefined behavior when\n used as a u32 shift count.\n- CTA_FILTER_ORIG_FLAGS/REPLY_FLAGS: use NLA_POLICY_MASK with\n CTA_FILTER_F_ALL, removing the manual mask checks.\n- CTA_EXPECT_FLAGS: use NLA_POLICY_MASK with NF_CT_EXPECT_MASK, adding\n a new mask define grouping all valid expect flags.\n\nExtracted from a broader nf-next patch by Florian Westphal, scoped to\nctnetlink for the fixes tree."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.253", "versionStartIncluding": "2.6.22"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.203", "versionStartIncluding": "2.6.22"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.168", "versionStartIncluding": "2.6.22"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.131", "versionStartIncluding": "2.6.22"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.80", "versionStartIncluding": "2.6.22"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.18.21", "versionStartIncluding": "2.6.22"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.19.11", "versionStartIncluding": "2.6.22"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.0", "versionStartIncluding": "2.6.22"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T22:09:50.284Z"}}}, "cveMetadata": {"cveId": "CVE-2026-31495", "state": "PUBLISHED", "dateUpdated": "2026-11-10T12:44:37.122Z", "dateReserved": "2026-03-09T15:48:24.102Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2026-04-22T13:54:17.591Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

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The normal TCP option parsing path already clamps to this value,\n but the ctnetlink path accepted 0-255, causing undefined behavior when\n used as a u32 shift count.\n- CTA_FILTER_ORIG_FLAGS/REPLY_FLAGS: use NLA_POLICY_MASK with\n CTA_FILTER_F_ALL, removing the manual mask checks.\n- CTA_EXPECT_FLAGS: use NLA_POLICY_MASK with NF_CT_EXPECT_MASK, adding\n a new mask define grouping all valid expect flags.\n\nExtracted from a broader nf-next patch by Florian Westphal, scoped to\nctnetlink for the fixes tree."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnetfilter: ctnetlink: utilizar comprobaciones de rango de pol\u00edtica de netlink\n\nReemplazar las validaciones manuales de rango y m\u00e1scara con anotaciones de pol\u00edtica de netlink en las rutas de c\u00f3digo de ctnetlink, para que el n\u00facleo de netlink rechace los valores no v\u00e1lidos tempranamente y pueda generar errores extack.\n\n- CTA_PROTOINFO_TCP_STATE: rechazar valores > TCP_CONNTRACK_SYN_SENT2 a nivel de pol\u00edtica, eliminando la comprobaci\u00f3n manual >= TCP_CONNTRACK_MAX.\n- CTA_PROTOINFO_TCP_WSCALE_ORIGINAL/REPLY: rechazar valores > TCP_MAX_WSCALE (14). La ruta normal de an\u00e1lisis de opciones TCP ya se ajusta a este valor, pero la ruta de ctnetlink aceptaba 0-255, causando un comportamiento indefinido cuando se usaba como un contador de desplazamiento u32.\n- CTA_FILTER_ORIG_FLAGS/REPLY_FLAGS: usar NLA_POLICY_MASK con CTA_FILTER_F_ALL, eliminando las comprobaciones manuales de m\u00e1scara.\n- CTA_EXPECT_FLAGS: usar NLA_POLICY_MASK con NF_CT_EXPECT_MASK, a\u00f1adiendo una nueva definici\u00f3n de m\u00e1scara que agrupa todas las banderas de expectaci\u00f3n v\u00e1lidas.\n\nExtra\u00eddo de un parche nf-next m\u00e1s amplio por Florian Westphal, delimitado a ctnetlink para el \u00e1rbol de correcciones."}], "id": "CVE-2026-31495", "lastModified": "2026-11-11T23:10:00.263", "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-2026-31495", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-11-05T21:35:22.554497Z", "version": "2.0.3"}}]}, "published": "2026-04-22T14:16:47.500", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2ef71307c86a9f866d6e28f1a0c06e2e9d794474"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/435b576cd2faa75154777868f8cbb73bf71644d3"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/45c33e79ae705b7af97e3117672b6cd258dd0b1b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/4f7d25f3f0786402ba48ff7d13b6241d77d975f5"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/675c913b940488a84effdeeac5a1cfb657b59804"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/8f15b5071b4548b0aafc03b366eb45c9c6566704"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c6cb41eaae875501eaaa487b8db6539feb092292"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/fcec5ce2d73a41668b24e3f18c803541602a59f6"}, {"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-082556.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"}]}

{"bugzilla": {"description": "kernel: netfilter: ctnetlink: use netlink policy range checks", "id": "2460664", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2460664"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-1287", "details": ["A flaw was found in the Linux kernel's netfilter connection tracking (ctnetlink) component. This vulnerability, related to improper input validation, allows an attacker to provide malformed netlink policy attributes. Specifically, invalid values for TCP window scaling (WSCALE) could lead to undefined behavior within the kernel. This could result in a system crash, causing a Denial of Service (DoS) for affected systems."], "name": "CVE-2026-31495", "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": "Out of support scope", "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": "2026-04-22T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-31495\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31495\nhttps://lore.kernel.org/linux-cve-announce/2026042203-CVE-2026-31495-f86b@gregkh/T"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4,435b576cd2faa75154777868f8cbb73bf71644d3)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4,2ef71307c86a9f866d6e28f1a0c06e2e9d794474)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4,4f7d25f3f0786402ba48ff7d13b6241d77d975f5)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4,fcec5ce2d73a41668b24e3f18c803541602a59f6)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4,675c913b940488a84effdeeac5a1cfb657b59804)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4,c6cb41eaae875501eaaa487b8db6539feb092292)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4,45c33e79ae705b7af97e3117672b6cd258dd0b1b)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[c8e2078cfe414a99cf6f2f2f1d78c7e75392e9d4,8f15b5071b4548b0aafc03b366eb45c9c6566704)"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "2.6.22"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[0,2.6.22)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,5.10.*]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,5.15.*]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,6.1.*]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,6.6.*]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,6.12.*]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,6.18.*]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,6.19.*]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[0,*]"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "analysis": {"en": {"generated_at": "2026-04-28T20:53:49.882008+00:00", "value": {"mitigation_remediation": ["Upgrade the Linux kernel to a version that includes the ctnetlink netlink policy range check patch (commit 2ef71307c86a9f866d6e28f1a0c06e2e9d794474 or later).", "If an immediate kernel upgrade is impractical, restrict access to the ctnetlink Netlink interface so that only privileged users may send messages, or disable the interface altogether if it is not required.", "Continuously monitor kernel logs (e.g., dmesg, /var/log/kern.log) for indications of Netlink\u2011related crashes or abnormal activity, and investigate any suspicious entries promptly."], "summary": {"action": "Apply Patch", "impact": "Denial of Service"}, "threat_synthesis": {"affected_systems": "All Linux kernel releases that contain the unpatched ctnetlink implementation. The fix was merged in commit 2ef71307c86a9f866d6e28f1a0c06e2e9d794474; any downstream distribution shipping a kernel prior to that commit is susceptible. The affected system type is the kernel itself, with no vendor\u2011specific product constraint beyond the Linux kernel.", "description_and_impact": "The vulnerability in the Linux kernel\u2019s ctnetlink code path arises from manual validation failures that permitted out\u2011of\u2011range values to be accepted by Netlink. In particular, the TCP window scale option previously accepted a shift count of 0-255, which is beyond the allowed maximum of 14. Using an illegal shift count can lead to undefined behavior and a kernel crash. The patch replaces these checks with Netlink policy annotations so that the kernel rejects such values at policy level, preventing the faulty code from executing.", "risk_and_exploitability": "The CVSS score of 5.5 indicates a moderate severity. The EPSS score is reported as less than 1%, showing a very low probability of exploitation in current deployments. The CVE is not listed in the CISA KEV catalog. The description does not explicitly state the required privilege level or whether the attack is local; based on the nature of the Netlink interface, the attack vector is inferred to be local or require elevated privileges. If an attacker can send malformed Netlink messages to ctnetlink, the kernel may crash, leading to a denial of service for the affected host."}}}}, "created": "2026-04-22T18:00:05.277909+00:00", "updated": "2026-04-28T21:00:14.762934+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}