{"id":"CVE-2026-64538","title":"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…","summary":"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…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= c0b220cf7d80eb8a36ae9f12cae6df4577a6814e < d08d019f2f43a6f9a71e81868bbc326b3afaf37b","Linux >= c0b220cf7d80eb8a36ae9f12cae6df4577a6814e < 1451deca9896957159f0666520a792c1b861af4f","Linux >= c0b220cf7d80eb8a36ae9f12cae6df4577a6814e < b2c70dd3326809429b709a9c7e9220d29923051a","Linux >= c0b220cf7d80eb8a36ae9f12cae6df4577a6814e < 302d57ed7872838b40e56a868fb4c7da7da606e9","Linux >= c0b220cf7d80eb8a36ae9f12cae6df4577a6814e < 80600b5d0f3ecb9324120dc95b5e915130f516c5","Linux >= c0b220cf7d80eb8a36ae9f12cae6df4577a6814e < b0d0eb13a0441a8ebf4f227843deaf494f1e2c33","Linux >= c0b220cf7d80eb8a36ae9f12cae6df4577a6814e < 6428634f7a0b7878144b4925c37856bef3224967","Linux >= c0b220cf7d80eb8a36ae9f12cae6df4577a6814e < 46c3b8191aad3d032776bf3bebf03efdf5f4b905","Linux 5.3"],"published":"2026-07-27","updated":"2026-09-08","sourceUpdated":"2026-09-08T09:18:19.810","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-64538","references":[{"url":"https://git.kernel.org/stable/c/1451deca9896957159f0666520a792c1b861af4f","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/302d57ed7872838b40e56a868fb4c7da7da606e9","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/46c3b8191aad3d032776bf3bebf03efdf5f4b905","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/6428634f7a0b7878144b4925c37856bef3224967","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/80600b5d0f3ecb9324120dc95b5e915130f516c5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b0d0eb13a0441a8ebf4f227843deaf494f1e2c33","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b2c70dd3326809429b709a9c7e9220d29923051a","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d08d019f2f43a6f9a71e81868bbc326b3afaf37b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html","label":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"}],"tags":["nvd","cve.org"],"epss":0.00243,"epssPercentile":0.1372,"ingestedAt":"2026-09-08T15:33:26.950Z","slug":"CVE-2026-64538","body":"## Overview\n\nIn 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\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}