{"id":"CVE-2026-64542","summary":"ipv6: ndisc: fix NULL deref in accept_untracked_na()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: ndisc: fix NULL deref in accept_untracked_na()\n\naccept_untracked_na() re-fetches the inet6_dev with __in6_dev_get(dev)\nand dereferences idev-\u003ecnf.accept_untracked_na without a NULL check,\neven though its only caller ndisc_recv_na() already fetched and\nNULL-checked idev for the same device.\n\nBoth reads of dev-\u003eip6_ptr run in the same RCU read-side critical\nsection, but a concurrent addrconf_ifdown() can clear dev-\u003eip6_ptr\nbetween them: lowering the MTU below IPV6_MIN_MTU calls addrconf_ifdown()\nwithout the synchronize_net() that orders the unregister path, so the\nre-fetch returns NULL and oopses:\n\n BUG: KASAN: null-ptr-deref in ndisc_recv_na (net/ipv6/ndisc.c:974)\n Read of size 4 at addr 0000000000000364\n Call Trace:\n  \u003cIRQ\u003e\n  ndisc_recv_na (net/ipv6/ndisc.c:974)\n  icmpv6_rcv (net/ipv6/icmp.c:1193)\n  ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:479)\n  ip6_input_finish (net/ipv6/ip6_input.c:534)\n  ip6_input (net/ipv6/ip6_input.c:545)\n  ip6_mc_input (net/ipv6/ip6_input.c:635)\n  ipv6_rcv (net/ipv6/ip6_input.c:351)\n  \u003c/IRQ\u003e\n\nIt is reachable by an unprivileged user via a network namespace.\n\nPass the caller's already validated idev instead of re-fetching it; the\nidev stays alive for the whole RCU critical section, so it is safe even\nafter dev-\u003eip6_ptr has been cleared.","modified":"2026-08-21T03:30:23.978999414Z","published":"2026-07-27T20:10:34.994Z","related":["openSUSE-SU-2026:11476-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64542.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/160d3f0d7a556ceae505dcab521a37057b4ce28f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/62c719203cb521b64fab74da94a81bdde5c18808"},{"type":"WEB","url":"https://git.kernel.org/stable/c/63d1c23764de2309cedbb779c75188d257a09d9b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a6450f7cfae57b382cbaf66a577765c9a88b3c58"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d186e942365acece7c56d39da05dd63bf95b280a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e5ba3017e46f275ad347e762e8eecacec5efa41d"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64542.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64542"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"aaa5f515b16b6b3e137779ffb4c9558bb58c1e75"},{"fixed":"e5ba3017e46f275ad347e762e8eecacec5efa41d"},{"fixed":"160d3f0d7a556ceae505dcab521a37057b4ce28f"},{"fixed":"62c719203cb521b64fab74da94a81bdde5c18808"},{"fixed":"a6450f7cfae57b382cbaf66a577765c9a88b3c58"},{"fixed":"63d1c23764de2309cedbb779c75188d257a09d9b"},{"fixed":"d186e942365acece7c56d39da05dd63bf95b280a"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64542.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.0.0"},{"fixed":"6.1.183"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.148"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.97"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.40"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64542.json"}}],"schema_version":"1.9.0"}