{"id":"CVE-2026-63921","revision":null,"records":[{"revision":"1b4aa1a1ced94ea29f36d500ba53c4ec","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-63921","aliases":[],"title":"ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().\n\nAfter patch 1/2 in this series, vti6_update() unlinks and relinks\nthe tunnel through t->net. vti6_siocdevprivate() still uses\ndev_net(dev) for the collision lookup. For a tunnel moved through\nIFLA_NET_NS_FD, dev_net(dev) is the new netns, not t->net.\n\nSIOCCHGTUNNEL on a migrated tunnel then runs:\n\n net = dev_net(dev) /* migrated netns */\n t = vti6_locate(net, &p1, false) /* misses target in t->net */\n ...\n t = netdev_priv(dev)\n vti6_update(t, &p1, false) /* mutates t->net's hash */\n\nA caller in the migrated netns picks params that match a tunnel\nin the creation netns. The lookup in dev_net(dev) finds nothing.\nvti6_update() prepends the migrated tunnel at the head of the\ncreation netns hash bucket for those params. Later lookups in\nthe creation netns resolve to the migrated device. xfrm receive\ndelivers the matched packets through a device the caller controls.\n\nReachable from an unprivileged user namespace (unshare --user\n--map-root-user --net). Cross tenant scope on container hosts.\n\nSwitch the SIOCCHGTUNNEL path on a non fallback device to use\nt->net for the lookup. The lookup now matches the netns\nvti6_update() operates on.\n\nAlso add ns_capable(self->net->user_ns, CAP_NET_ADMIN) before\nthe lookup. The check at the top of the case is against\ndev_net(dev)->user_ns, which after migration is the attacker's\nnetns. A caller there can pick params absent from self->net,\nthe lookup returns NULL, t becomes self, and vti6_update()\ninserts the device into the creation netns hash. The new check\nrequires CAP_NET_ADMIN in the creation netns user_ns too.\n\nSIOCADDTUNNEL and SIOCCHGTUNNEL on the fallback device keep\ndev_net(dev), which equals init_net there.","state":0,"publishedAt":"2026-07-19T14:55:23.539+00:00","modifiedAt":"2026-10-19T20:17:56.432+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/ip6_vti.c\"\n ],\n \"versions\": [\n {\n \"version\": \"61220ab349485d911083d0b7990ccd3db6c63297\",\n \"lessThan\": \"94ff740a7f9ef5c010784a325dca00cbf228f941\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"61220ab349485d911083d0b7990ccd3db6c63297\",\n \"lessThan\": \"df42ac708acc3399bbb6dc5ca16e0540adda7bbf\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"61220ab349485d911083d0b7990ccd3db6c63297\",\n \"lessThan\": \"44d2ff7d2178503b93151140a45dfa2ad49c9906\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"61220ab349485d911083d0b7990ccd3db6c63297\",\n \"lessThan\": \"1acfb7d9c6fc7e209ed7789392697e97e03edd33\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"61220ab349485d911083d0b7990ccd3db6c63297\",\n \"lessThan\": \"d2236348414bdd6558385f35aa7fdc9bf5634011\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"61220ab349485d911083d0b7990ccd3db6c63297\",\n \"lessThan\": \"853f6ea482dfcd3404bbef458ab4d68364eed838\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"61220ab349485d911083d0b7990ccd3db6c63297\",\n \"lessThan\": \"596f6354c96a891e58c04a09cbfb7b0d1ec00dab\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"61220ab349485d911083d0b7990ccd3db6c63297\",\n \"lessThan\": \"8b484efd5cb4eeef9021a661e198edc5349dacf6\",\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/ip6_vti.c\"\n ],\n \"versions\": [\n {\n \"version\": \"3.15\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"3.15\",\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:C/C:H/I:H/A:H","score":8.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/94ff740a7f9ef5c010784a325dca00cbf228f941","https://git.kernel.org/stable/c/df42ac708acc3399bbb6dc5ca16e0540adda7bbf","https://git.kernel.org/stable/c/44d2ff7d2178503b93151140a45dfa2ad49c9906","https://git.kernel.org/stable/c/1acfb7d9c6fc7e209ed7789392697e97e03edd33","https://git.kernel.org/stable/c/d2236348414bdd6558385f35aa7fdc9bf5634011","https://git.kernel.org/stable/c/853f6ea482dfcd3404bbef458ab4d68364eed838","https://git.kernel.org/stable/c/596f6354c96a891e58c04a09cbfb7b0d1ec00dab","https://git.kernel.org/stable/c/8b484efd5cb4eeef9021a661e198edc5349dacf6"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-63921","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-63921","identifiers":["CVE-2026-63921"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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