{"id":"CVE-2026-64538","state":"PUBLISHED","title":"ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix null-ptr-deref in fib6_nh_mtu_change().\n\nfib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and\ndereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown()\nclears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has\nreleased tb6_lock, so the RA-driven MTU walk can observe a NULL idev and\noops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(),\nbut this re-fetch is unguarded; nexthop-backed routes survive\naddrconf_ifdown()'s flush, so the walk still reaches it after ip6_ptr is\nnulled.\n\nReturn 0 when idev is NULL, matching rt6_mtu_change_route() and the\nfib6_mtu() fix in commit 5ad509c1fdad (\"ipv6: Fix null-ptr-deref in\nfib6_mtu().\").\n\n  Oops: general protection fault, ... KASAN: null-ptr-deref in range\n        [0x00000000000002a8-0x00000000000002af]\n  RIP: 0010:fib6_nh_mtu_change+0x203/0x990\n   rt6_mtu_change_route+0x141/0x1d0\n   __fib6_clean_all+0xd0/0x160\n   rt6_mtu_change+0xb4/0x100\n   ndisc_router_discovery+0x24b5/0x2cb0\n   icmpv6_rcv+0x12e9/0x1710\n   ipv6_rcv+0x39b/0x410","publishedAt":"2026-07-27T20:10:32.779Z","updatedAt":"2026-10-15T01:23:51.777Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","status":"affected","lessThan":"d08d019f2f43a6f9a71e81868bbc326b3afaf37b","versionType":"git"},{"version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","status":"affected","lessThan":"1451deca9896957159f0666520a792c1b861af4f","versionType":"git"},{"version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","status":"affected","lessThan":"b2c70dd3326809429b709a9c7e9220d29923051a","versionType":"git"},{"version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","status":"affected","lessThan":"302d57ed7872838b40e56a868fb4c7da7da606e9","versionType":"git"},{"version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","status":"affected","lessThan":"80600b5d0f3ecb9324120dc95b5e915130f516c5","versionType":"git"},{"version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","status":"affected","lessThan":"b0d0eb13a0441a8ebf4f227843deaf494f1e2c33","versionType":"git"},{"version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","status":"affected","lessThan":"6428634f7a0b7878144b4925c37856bef3224967","versionType":"git"},{"version":"c0b220cf7d80eb8a36ae9f12cae6df4577a6814e","status":"affected","lessThan":"46c3b8191aad3d032776bf3bebf03efdf5f4b905","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/route.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv6/route.c"]}],"references":["https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b","https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f","https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a","https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9","https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5","https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33","https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967","https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905","https://cert-portal.siemens.com/productcert/html/ssa-019113.html","https://cert-portal.siemens.com/productcert/html/ssa-457936.html"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64538.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64538","state":"PUBLISHED","datePublished":"2026-07-27T20:10:32.779Z","dateUpdated":"2026-10-15T01:23:51.777Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T15:36:31.795Z"},"containers":{"cna":{"title":"ipv6: Fix null-ptr-deref in fib6_nh_mtu_change().","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: Fix null-ptr-deref in fib6_nh_mtu_change().\n\nfib6_nh_mtu_change() re-fetches idev via __in6_dev_get(arg->dev) and\ndereferences idev->cnf.mtu6 without a NULL check. addrconf_ifdown()\nclears dev->ip6_ptr with RCU_INIT_POINTER() after rt6_disable_ip() has\nreleased tb6_lock, so the RA-driven MTU walk can observe a NULL idev and\noops. The caller rt6_mtu_change_route() guards its own __in6_dev_get(),\nbut this re-fetch is unguarded; nexthop-backed routes survive\naddrconf_ifdown()'s flush, so the walk still reaches it after ip6_ptr is\nnulled.\n\nReturn 0 when idev is NULL, matching rt6_mtu_change_route() and the\nfib6_mtu() fix in commit 5ad509c1fdad (\"ipv6: Fix null-ptr-deref in\nfib6_mtu().\").\n\n  Oops: general protection fault, ... 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