{"api_version":"1","generated_at":"2026-07-22T08:15:48+00:00","cve":"CVE-2026-63921","urls":{"html":"https://cve.report/CVE-2026-63921","api":"https://cve.report/api/cve/CVE-2026-63921.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-63921","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63921"},"summary":{"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":"PUBLISHED","assigner":"Linux","published_at":"2026-07-19 16:17:10","updated_at":"2026-07-20 15:16:56"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"8.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"8.8","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","data":{"baseScore":8.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/df42ac708acc3399bbb6dc5ca16e0540adda7bbf","name":"https://git.kernel.org/stable/c/df42ac708acc3399bbb6dc5ca16e0540adda7bbf","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/8b484efd5cb4eeef9021a661e198edc5349dacf6","name":"https://git.kernel.org/stable/c/8b484efd5cb4eeef9021a661e198edc5349dacf6","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/1acfb7d9c6fc7e209ed7789392697e97e03edd33","name":"https://git.kernel.org/stable/c/1acfb7d9c6fc7e209ed7789392697e97e03edd33","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/94ff740a7f9ef5c010784a325dca00cbf228f941","name":"https://git.kernel.org/stable/c/94ff740a7f9ef5c010784a325dca00cbf228f941","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/853f6ea482dfcd3404bbef458ab4d68364eed838","name":"https://git.kernel.org/stable/c/853f6ea482dfcd3404bbef458ab4d68364eed838","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/596f6354c96a891e58c04a09cbfb7b0d1ec00dab","name":"https://git.kernel.org/stable/c/596f6354c96a891e58c04a09cbfb7b0d1ec00dab","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d2236348414bdd6558385f35aa7fdc9bf5634011","name":"https://git.kernel.org/stable/c/d2236348414bdd6558385f35aa7fdc9bf5634011","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/44d2ff7d2178503b93151140a45dfa2ad49c9906","name":"https://git.kernel.org/stable/c/44d2ff7d2178503b93151140a45dfa2ad49c9906","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63921","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63921","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61220ab349485d911083d0b7990ccd3db6c63297 94ff740a7f9ef5c010784a325dca00cbf228f941 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61220ab349485d911083d0b7990ccd3db6c63297 df42ac708acc3399bbb6dc5ca16e0540adda7bbf git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61220ab349485d911083d0b7990ccd3db6c63297 44d2ff7d2178503b93151140a45dfa2ad49c9906 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61220ab349485d911083d0b7990ccd3db6c63297 1acfb7d9c6fc7e209ed7789392697e97e03edd33 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61220ab349485d911083d0b7990ccd3db6c63297 d2236348414bdd6558385f35aa7fdc9bf5634011 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61220ab349485d911083d0b7990ccd3db6c63297 853f6ea482dfcd3404bbef458ab4d68364eed838 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61220ab349485d911083d0b7990ccd3db6c63297 596f6354c96a891e58c04a09cbfb7b0d1ec00dab git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 61220ab349485d911083d0b7990ccd3db6c63297 8b484efd5cb4eeef9021a661e198edc5349dacf6 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3.15","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 3.15 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.10.259 5.10.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.210 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.176 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.143 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.93 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.35 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.0.12 7.0.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"63921","cve":"CVE-2026-63921","epss":"0.002200000","percentile":"0.125280000","score_date":"2026-07-20","updated_at":"2026-07-21 00:13:13"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/ipv6/ip6_vti.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"94ff740a7f9ef5c010784a325dca00cbf228f941","status":"affected","version":"61220ab349485d911083d0b7990ccd3db6c63297","versionType":"git"},{"lessThan":"df42ac708acc3399bbb6dc5ca16e0540adda7bbf","status":"affected","version":"61220ab349485d911083d0b7990ccd3db6c63297","versionType":"git"},{"lessThan":"44d2ff7d2178503b93151140a45dfa2ad49c9906","status":"affected","version":"61220ab349485d911083d0b7990ccd3db6c63297","versionType":"git"},{"lessThan":"1acfb7d9c6fc7e209ed7789392697e97e03edd33","status":"affected","version":"61220ab349485d911083d0b7990ccd3db6c63297","versionType":"git"},{"lessThan":"d2236348414bdd6558385f35aa7fdc9bf5634011","status":"affected","version":"61220ab349485d911083d0b7990ccd3db6c63297","versionType":"git"},{"lessThan":"853f6ea482dfcd3404bbef458ab4d68364eed838","status":"affected","version":"61220ab349485d911083d0b7990ccd3db6c63297","versionType":"git"},{"lessThan":"596f6354c96a891e58c04a09cbfb7b0d1ec00dab","status":"affected","version":"61220ab349485d911083d0b7990ccd3db6c63297","versionType":"git"},{"lessThan":"8b484efd5cb4eeef9021a661e198edc5349dacf6","status":"affected","version":"61220ab349485d911083d0b7990ccd3db6c63297","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/ipv6/ip6_vti.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"3.15"},{"lessThan":"3.15","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.10.*","status":"unaffected","version":"5.10.259","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.210","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.176","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.143","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.93","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.35","versionType":"semver"},{"lessThanOrEqual":"7.0.*","status":"unaffected","version":"7.0.12","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.1","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.10.259","versionStartIncluding":"3.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.210","versionStartIncluding":"3.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.176","versionStartIncluding":"3.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.143","versionStartIncluding":"3.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.93","versionStartIncluding":"3.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.35","versionStartIncluding":"3.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.0.12","versionStartIncluding":"3.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1","versionStartIncluding":"3.15","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"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."}],"metrics":[{"cvssV3_1":{"baseScore":8.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-07-20T13:41:31.106Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/94ff740a7f9ef5c010784a325dca00cbf228f941"},{"url":"https://git.kernel.org/stable/c/df42ac708acc3399bbb6dc5ca16e0540adda7bbf"},{"url":"https://git.kernel.org/stable/c/44d2ff7d2178503b93151140a45dfa2ad49c9906"},{"url":"https://git.kernel.org/stable/c/1acfb7d9c6fc7e209ed7789392697e97e03edd33"},{"url":"https://git.kernel.org/stable/c/d2236348414bdd6558385f35aa7fdc9bf5634011"},{"url":"https://git.kernel.org/stable/c/853f6ea482dfcd3404bbef458ab4d68364eed838"},{"url":"https://git.kernel.org/stable/c/596f6354c96a891e58c04a09cbfb7b0d1ec00dab"},{"url":"https://git.kernel.org/stable/c/8b484efd5cb4eeef9021a661e198edc5349dacf6"}],"title":"ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-63921","datePublished":"2026-07-19T14:55:23.539Z","dateReserved":"2026-07-19T07:54:57.020Z","dateUpdated":"2026-07-20T13:41:31.106Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-07-19 16:17:10","lastModifiedDate":"2026-07-20 15:16:56","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","baseScore":8.8,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":2,"impactScore":6}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"63921","Ordinal":"1","Title":"ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().","CVE":"CVE-2026-63921","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"63921","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate()."}]}}}