{"id":"CVE-2026-63920","revision":null,"records":[{"revision":"aa9cd2052419414d9c19c4b5778c6838","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-63920","aliases":[],"title":"ipv6: validate extension header length before copying to cmsg","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: validate extension header length before copying to cmsg\n\nip6_datagram_recv_specific_ctl() builds IPV6_{HOPOPTS,DSTOPTS,RTHDR}\ncmsgs (and their IPV6_2292* legacy counterparts) by trusting the\non-wire hdrlen byte (ptr[1]) when computing the put_cmsg() length.\nThe length was validated only at parse time (ipv6_parse_hopopts(),\netc.). An nftables payload-write expression can rewrite hdrlen after\nparsing and before the skb reaches recvmsg; the write itself is\nin-bounds but put_cmsg() then reads up to ((hdrlen+1) << 3) = 2040\nbytes from an 8-byte header. nftables is reachable from an\nunprivileged user namespace, so this is an unprivileged\nslab-out-of-bounds read:\n\n BUG: KASAN: slab-out-of-bounds in put_cmsg+0x3ac/0x540\n put_cmsg+0x3ac/0x540\n udpv6_recvmsg+0xca0/0x1250\n sock_recvmsg+0xdf/0x190\n ____sys_recvmsg+0x1b1/0x620\n\nAdd ipv6_get_exthdr_len() which validates that at least two bytes\nare accessible before reading the hdrlen field, then checks the\ncomputed length against skb_tail_pointer(skb), returning 0 on\nfailure. Extension headers are kept in the linear skb area by\npskb_may_pull() during input, so skb_tail_pointer() is the correct\nbound.\n\nUse ipv6_get_exthdr_len() at all non-AH call sites: the five\nstandalone cmsg blocks (HbH, 2292HbH, 2292DSTOPTS x2, 2292RTHDR)\nand the three standard cases in the extension-header walk loop\n(DSTOPTS, ROUTING, default). AH retains an inline bounds check\nbecause its length formula differs ((ptr[1]+2)<<2).\n\nThe walk loop also gets a pre-read bounds check at the top to\nvalidate ptr before any case accesses ptr[0] or ptr[1].\n\nWhen the walk loop detects a corrupted header, return from the\nfunction instead of continuing to process later socket options.","state":0,"publishedAt":"2026-07-19T14:55:22.813+00:00","modifiedAt":"2026-10-19T20:17:56.265+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"net/ipv6/datagram.c\"\n ],\n \"versions\": [\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"81394827dfb72772c50d0ae3bdfa094428a5d76d\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"931b4a1f13408c2507719890f78f7227c34a0282\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"08464413e628803bd10cb1df68d0138665f2f885\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"a29768d56eb3798c052ad3281b05596e695a17af\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"0d330eff318c0f44d4fb0ad2c2aef38f87f24c90\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"a35daeabb433686234b010ebf7b53778dbd6c9b8\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"eb18a1b1644e4cad978df2131e2bb9a2e6886992\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n \"lessThan\": \"dd433671fef381fdaf7b530c631e6b782d66e224\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"net/ipv6/datagram.c\"\n ],\n \"versions\": [\n {\n \"version\": \"2.6.12\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"2.6.12\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.259\",\n \"lessThanOrEqual\": \"5.10.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.210\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.176\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.143\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.93\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.35\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.0.12\",\n \"lessThanOrEqual\": \"7.0.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.1\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","score":7.1,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/81394827dfb72772c50d0ae3bdfa094428a5d76d","https://git.kernel.org/stable/c/931b4a1f13408c2507719890f78f7227c34a0282","https://git.kernel.org/stable/c/08464413e628803bd10cb1df68d0138665f2f885","https://git.kernel.org/stable/c/a29768d56eb3798c052ad3281b05596e695a17af","https://git.kernel.org/stable/c/0d330eff318c0f44d4fb0ad2c2aef38f87f24c90","https://git.kernel.org/stable/c/a35daeabb433686234b010ebf7b53778dbd6c9b8","https://git.kernel.org/stable/c/eb18a1b1644e4cad978df2131e2bb9a2e6886992","https://git.kernel.org/stable/c/dd433671fef381fdaf7b530c631e6b782d66e224"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63920","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-63920","identifiers":["CVE-2026-63920"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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Not a global EUVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-f1b70ba09149408c9b3f93f80725b8b9","complete":true,"records":13654,"lastAttemptAt":"2026-11-08T19:48:04.0257169+00:00","lastSuccessAt":"2026-11-08T19:48:04.022+00:00","error":null,"lastVerifiedAt":"2026-11-08T19:48:04.022+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13706,"expectedIdentifiers":13706,"failedIdentifiers":0},{"source":"first-epss:nuget","scope":"FIRST EPSS for explicit CVE aliases in the collected public NuGet archive. Not a global EPSS backfill.","generation":"2026-11-08T19:47:20.1649891+00:00","complete":true,"records":1096,"lastAttemptAt":"2026-11-08T19:47:20.1649891+00:00","lastSuccessAt":"2026-11-08T19:47:20.3951142+00:00","error":null,"lastVerifiedAt":"2026-11-08T19:47:20.3951146+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"nvd","scope":"Rolling NVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. Not a global NVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-3b79c659b4ac42b2801e63ff6ff3a882","complete":false,"records":13666,"lastAttemptAt":"2026-11-08T19:47:46.1695591+00:00","lastSuccessAt":"2026-11-08T19:47:46.166+00:00","error":null,"lastVerifiedAt":"2026-11-08T19:47:46.166+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13206,"expectedIdentifiers":13706,"failedIdentifiers":0},{"source":"osv:Go","scope":"Complete OSV Go ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"go-980593e6977a6d1b4fb1eed5a1ffe88a468736f89f0a06f710924ad59132c023","complete":true,"records":9914,"lastAttemptAt":"2026-11-08T19:47:20.0165357+00:00","lastSuccessAt":"2026-11-08T11:07:07.068788+00:00","error":null,"lastVerifiedAt":"2026-11-08T19:47:20.0165357+00:00","snapshotPublishedAt":"2026-11-08T11:02:46+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:NuGet","scope":"Complete OSV NuGet ecosystem archive, including GitHub Advisory Database records; NuGet version matching only","generation":"nuget-fde804134ecdda0ddd5ff5c26ee1fff5a6fa659311f7ef2e51c6ad54964db0e2","complete":true,"records":1971,"lastAttemptAt":"2026-11-08T19:47:19.7560084+00:00","lastSuccessAt":"2026-11-06T19:03:17.0399903+00:00","error":null,"lastVerifiedAt":"2026-11-08T19:47:19.7560084+00:00","snapshotPublishedAt":"2026-11-06T18:17:57+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:crates.io","scope":"Complete OSV crates.io ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"crates.io-964c14035e6f0f6478b2870fad6a7ef9f6045876d4a12af2c2e514521e54b6af","complete":true,"records":3055,"lastAttemptAt":"2026-11-08T19:47:20.1181272+00:00","lastSuccessAt":"2026-11-08T11:07:12.1927025+00:00","error":null,"lastVerifiedAt":"2026-11-08T19:47:20.1181272+00:00","snapshotPublishedAt":"2026-11-08T11:02:46+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:npm","scope":"Complete OSV npm ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"npm-f8647d7ba64b1ba0dfdc7130944766d5b36d5b77d18fff0c79e651a4cff3c2b9","complete":true,"records":231293,"lastAttemptAt":"2026-11-08T19:47:19.9161497+00:00","lastSuccessAt":"2026-11-08T11:06:56.2918717+00:00","error":null,"lastVerifiedAt":"2026-11-08T19:47:19.9161497+00:00","snapshotPublishedAt":"2026-11-08T11:02:50+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null}]}