{"id":"CVE-2026-74561","summary":"nexthop: avoid unlocked f6i_list walk in nh_rt_cache_flush","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnexthop: avoid unlocked f6i_list walk in nh_rt_cache_flush\n\nnh_rt_cache_flush() walks nh-\u003ef6i_list during an RTNL-serialized nexthop\nreplace without holding nh-\u003elock, racing the unlocked IPv6 route\nadd/delete that mutate the list under nh-\u003elock and free fib6_info\nentries (nh_rt_cache_flush() is inlined into rtm_new_nexthop()):\n\n  BUG: KASAN: slab-use-after-free in nh_rt_cache_flush (net/ipv4/nexthop.c:2243)\n  Read of size 8 at addr ffff888012953e18 by task exploit/146\n   nh_rt_cache_flush (net/ipv4/nexthop.c:2243)\n   replace_nexthop (net/ipv4/nexthop.c:2610)\n   rtm_new_nexthop (net/ipv4/nexthop.c:3323)\n   rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)\n\nUnlike the other f6i_list walks, this one bumps each route's sernum via\nfib6_update_sernum_upto_root(), which needs tb6_lock; taking nh-\u003elock\naround it would invert the established tb6_lock -\u003e nh-\u003elock order and\ndeadlock. As the only purpose is to invalidate cached dsts, bump the\nIPv6 sernum for the whole netns with rt_genid_bump_ipv6() instead,\nmirroring the rt_cache_flush() already done for IPv4 just above.","modified":"2026-08-18T03:56:30.682763276Z","published":"2026-08-15T12:28:04.525Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74561.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/44f53e4331a30fabc38a411fae7524341b618db3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4787a6d2629b4e8c0b6bacab1f75c1660eca44d9"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74561.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74561"},{"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":"081efd18326e353c6fbfdeff903a83edde953f72"},{"fixed":"44f53e4331a30fabc38a411fae7524341b618db3"},{"fixed":"4787a6d2629b4e8c0b6bacab1f75c1660eca44d9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74561.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.16.0"},{"fixed":"7.1.8"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74561.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"}]}