{"api_version":"1","generated_at":"2026-08-22T04:33:46+00:00","cve":"CVE-2026-72137","urls":{"html":"https://cve.report/CVE-2026-72137","api":"https://cve.report/api/cve/CVE-2026-72137.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-72137","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-72137"},"summary":{"title":"xfrm: nat_keepalive: avoid double free on send error","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: nat_keepalive: avoid double free on send error\n\nnat_keepalive_send() frees the keepalive skb whenever the IPv4 or IPv6\nsend helper reports an error.\n\nThat cleanup is only correct before the skb is handed to the output\npath. Once ip_build_and_send_pkt() or ip6_xmit() takes ownership, the\nnetworking stack may already have consumed the skb before returning an\nerror, so freeing it again is unsafe.\n\nHandle the pre-handoff failure cases inside nat_keepalive_send_ipv4()\nand nat_keepalive_send_ipv6(), where the caller still owns the skb, and\nkeep nat_keepalive_send() responsible only for family dispatch and the\nunsupported-family cleanup path.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-15 06:21:31","updated_at":"2026-08-17 06:18:13"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/226f4a490d1a938fc838d8f8c46a4eca864c0d78","name":"https://git.kernel.org/stable/c/226f4a490d1a938fc838d8f8c46a4eca864c0d78","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693","name":"https://git.kernel.org/stable/c/a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/5b0c4c916f202b8fd13d12afb6af62b385622f81","name":"https://git.kernel.org/stable/c/5b0c4c916f202b8fd13d12afb6af62b385622f81","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d0a4dc7efa825bce60a8da8f7d43c864a159abde","name":"https://git.kernel.org/stable/c/d0a4dc7efa825bce60a8da8f7d43c864a159abde","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-72137","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72137","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae d0a4dc7efa825bce60a8da8f7d43c864a159abde git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae 5b0c4c916f202b8fd13d12afb6af62b385622f81 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f531d13bdfe3f4f084aaa8acae2cb0f02295f5ae 226f4a490d1a938fc838d8f8c46a4eca864c0d78 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: nat_keepalive: avoid double free on send error\n\nnat_keepalive_send() frees the keepalive skb whenever the IPv4 or IPv6\nsend helper reports an error.\n\nThat cleanup is only correct before the skb is handed to the output\npath. Once ip_build_and_send_pkt() or ip6_xmit() takes ownership, the\nnetworking stack may already have consumed the skb before returning an\nerror, so freeing it again is unsafe.\n\nHandle the pre-handoff failure cases inside nat_keepalive_send_ipv4()\nand nat_keepalive_send_ipv6(), where the caller still owns the skb, and\nkeep nat_keepalive_send() responsible only for family dispatch and the\nunsupported-family cleanup path."}],"metrics":[{"cvssV3_1":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:N - On internet-facing IPsec VPN gateways using kernel NAT keepalive, a remote attacker can induce post-handoff outbound send failures (e.g., ENOMEM from network-driven memory pressure) when periodic keepalives are transmitted, reaching the vulnerable double-free path.\nAC:L - After an outbound ESP-in-UDP SA has NAT keepalive configured, an attacker can reliably force send errors where the stack already consumed the skb (ip6_xmit EMSGSIZE, ip_finish_output2 neighbour/ENOMEM paths) without uncontrollable races or memory layout dependencies.\nPR:N - Remote exploitation requires no privileges on the victim; it only needs a typical IPsec NAT-T deployment where userspace already set XFRMA_NAT_KEEPALIVE_INTERVAL. Local exploitation via user namespaces needs only CAP_NET_ADMIN (PR:L), not root in the init namespace.\nUI:N - No victim or administrator interaction is needed during exploitation; NAT keepalives are sent automatically by the kernel delayed work queue on the configured interval once the XFRM SA exists.\nS:U - Impact is kernel heap corruption and privilege escalation within the same security authority; this is not a VM escape, container breakout, or IOMMU/DMA boundary bypass.\nC:H - The skb double-free corrupts the slab allocator and yields use-after-free primitives that can be leveraged for arbitrary kernel memory disclosure, not merely a bounded leak or crash-only NULL dereference.\nI:H - Double-free heap corruption enables attacker-controlled reallocation of freed sk_buff objects, supporting arbitrary kernel memory writes, control-flow hijacking, and local privilege escalation.\nA:H - The double-free reliably causes slab corruption, kernel oops, or panic during keepalive send-error cleanup, providing immediate and repeatable denial of service on affected systems."}]}],"providerMetadata":{"dateUpdated":"2026-08-17T05:40:47.767Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/d0a4dc7efa825bce60a8da8f7d43c864a159abde"},{"url":"https://git.kernel.org/stable/c/5b0c4c916f202b8fd13d12afb6af62b385622f81"},{"url":"https://git.kernel.org/stable/c/a8a7e6a9ff8a4c1f067694ddbd44be67fdf36693"},{"url":"https://git.kernel.org/stable/c/226f4a490d1a938fc838d8f8c46a4eca864c0d78"}],"title":"xfrm: nat_keepalive: avoid double free on send error","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-72137","datePublished":"2026-08-15T05:53:11.812Z","dateReserved":"2026-08-09T03:40:39.908Z","dateUpdated":"2026-08-17T05:40:47.767Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-15 06:21:31","lastModifiedDate":"2026-08-17 06:18:13","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"72137","Ordinal":"1","Title":"xfrm: nat_keepalive: avoid double free on send error","CVE":"CVE-2026-72137","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"72137","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: nat_keepalive: avoid double free on send error\n\nnat_keepalive_send() frees the keepalive skb whenever the IPv4 or IPv6\nsend helper reports an error.\n\nThat cleanup is only correct before the skb is handed to the output\npath. Once ip_build_and_send_pkt() or ip6_xmit() takes ownership, the\nnetworking stack may already have consumed the skb before returning an\nerror, so freeing it again is unsafe.\n\nHandle the pre-handoff failure cases inside nat_keepalive_send_ipv4()\nand nat_keepalive_send_ipv6(), where the caller still owns the skb, and\nkeep nat_keepalive_send() responsible only for family dispatch and the\nunsupported-family cleanup path.","Type":"Description","Title":"xfrm: nat_keepalive: avoid double free on send error"}]}}}