{"id":"CVE-2026-64581","summary":"xfrm: fix sk_dst_cache double-free in xfrm_user_policy()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: fix sk_dst_cache double-free in xfrm_user_policy()\n\nxfrm_user_policy() clears the socket dst cache with __sk_dst_reset(),\ni.e. the non-atomic __sk_dst_set(sk, NULL): it reads sk_dst_cache with\nrcu_dereference_protected(), stores NULL and dst_release()s the old dst.\nThat is only safe if no other thread modifies sk_dst_cache concurrently.\n\nFor a connected UDP socket that does not hold: the transmit fast path\n(udp_sendmsg -\u003e sk_dst_check -\u003e sk_dst_reset) resets the cache locklessly\nwith an atomic xchg(). A per-socket policy change racing a send can make\nboth sides observe the same old dst and each dst_release() it, dropping\nthe socket's single reference twice and freeing the xfrm_dst bundle while\nit is still referenced:\n\n  BUG: KASAN: slab-use-after-free in dst_release\n  Write of size 4 at addr ffff88801897b6c0 by task exploit/155\n  Call Trace:\n   ...\n   dst_release (... ./include/linux/rcuref.h:109)\n   xfrm_user_policy (./include/net/sock.h:2239 ./include/net/sock.h:2256 net/xfrm/xfrm_state.c:3053)\n   do_ip_setsockopt (net/ipv4/ip_sockglue.c:1347)\n   ip_setsockopt (net/ipv4/ip_sockglue.c:1417)\n   do_sock_setsockopt (net/socket.c:2368)\n   __sys_setsockopt (net/socket.c:2393)\n   __x64_sys_setsockopt (net/socket.c:2396)\n   do_syscall_64 (arch/x86/entry/syscall_64.c:94)\n   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)\n\nReachable by an unprivileged user via a user+network namespace.\n\nUse the atomic sk_dst_reset() so the cache is cleared and released with a\nsingle xchg(): whichever side wins releases the dst once, the other sees\nNULL and does nothing. Behaviour is otherwise unchanged.","modified":"2026-08-09T03:31:36.115352429Z","published":"2026-08-05T08:09:35.556Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64581.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/96b678d08268b5f5c6fc99d4289d9b7e334fc683"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c283e9ada7fcb7dd4b10592623086b2e6d2f9925"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64581.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64581"},{"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":"2b06cdf3e688b98fcc9945873b5d42792bd4eee0"},{"fixed":"96b678d08268b5f5c6fc99d4289d9b7e334fc683"},{"fixed":"c283e9ada7fcb7dd4b10592623086b2e6d2f9925"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0"},{"last_affected":"72f157be2f81910ae759bfe2e5c2256fc4625645"},{"last_affected":"9e9fe58a92a46c6d154d2901735bf230d91b8507"},{"last_affected":"adc1ec6cdc20d430aa01b86497220709b9149466"},{"last_affected":"b54033eb1cfd77aba471269ddd804ed8d3e35dea"},{"last_affected":"c9e82cb34c3c2ee895af01bc899c6ed0bc6eb04a"},{"last_affected":"5eef9b51114fcc65651d671add52f267f91b9451"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3.16.52"},{"fixed":"3.17"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.4.163"},{"fixed":"4.5"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3.18.101"},{"fixed":"3.19"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.1.52"},{"fixed":"4.2"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.4.123"},{"fixed":"4.5"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.9.89"},{"fixed":"4.10"}]}],"versions":["v4.4.162","v4.4.161","v4.4.160","v4.4.159","v4.4.158","v4.4.157","v4.4.156","v4.4.155","v4.4.154","v4.4.153","v4.4.152","v4.4.151","v4.4.150","v4.4.149","v4.4.148","v4.4.147","v4.4.146","v4.4.145","v4.4.144","v4.4.143","v4.4.142","v4.4.141","v4.4.140","v4.4.139","v4.4.138","v4.4.137","v4.4.136","v4.4.135","v4.4.134","v4.4.133","v4.4.132","v4.1.51","v4.4.131","v4.4.130","v4.4.129","v4.4.128","v4.4.127","v4.4.126","v4.4.125","v4.4.124","v4.4.123","v3.18.100","v4.4.122","v4.9.88","v4.1.50","v4.9.87","v4.4.121","v3.18.99","v4.9.86","v4.4.120","v3.18.98","v4.9.85","v4.4.119","v3.18.97","v4.1.49","v4.9.84","v4.4.118","v3.18.96","v4.9.83","v4.4.117","v3.18.95","v4.4.116","v4.9.82","v4.9.81","v3.18.94","v4.4.115","v4.9.80","v3.18.93","v4.9.79","v4.4.114","v3.18.92","v4.9.78","v4.4.113","v4.9.77","v4.4.112","v4.1.48","v4.9.76","v4.4.111","v3.18.91","v4.9.75","v4.4.110","v4.9.74","v4.4.109","v4.9.73","v4.4.108","v3.18.90","v3.16.51","v4.9.72","v4.9.71","v4.4.107","v3.18.89","v4.9.70","v4.4.106","v3.18.88","v4.9.69","v4.4.105","v3.18.87","v4.9.68","v4.9.67","v4.4.104","v3.18.86","v4.1.47","v4.1.46","v4.9.66","v4.4.103","v3.18.85","v4.9.65","v4.4.102","v3.18.84","v3.16.50","v4.4.101","v4.9.64","v4.4.100","v3.18.83","v4.9.63","v4.4.99","v3.18.82","v4.9.62","v4.4.98","v3.18.81","v4.4.97","v4.9.61","v3.18.80","v3.16.49","v4.9.60","v4.4.96","v3.18.79","v4.1.45","v4.9.59","v4.4.95","v3.18.78","v4.9.58","v4.4.94","v3.18.77","v4.9.57","v4.4.93","v3.18.76","v4.9.56","v4.4.92","v3.18.75","v4.9.55","v3.16.48","v4.9.54","v4.4.91","v3.18.74","v4.9.53","v4.4.90","v3.18.73","v4.9.52","v4.4.89","v3.18.72","v4.1.44","v4.9.51","v4.4.88","v3.18.71","v4.9.50","v3.16.47","v4.9.49","v4.4.87","v3.18.70","v4.9.48","v4.9.47","v4.4.86","v3.18.69","v4.9.46","v4.4.85","v3.18.68","v4.1.43","v4.9.45","v4.4.84","v3.18.67","v3.16.46","v4.9.44","v4.4.83","v3.18.66","v4.9.43","v4.4.82","v3.18.65","v4.9.42","v4.4.81","v3.18.64","v3.18.63","v4.4.80","v4.9.41","v4.4.79","v4.9.40","v4.9.39","v4.4.78","v3.18.62","v4.1.42","v3.18.61","v4.4.77","v4.9.38","v3.16.45","v4.9.37","v4.4.76","v3.18.60","v4.9.36","v4.9.35","v4.4.75","v3.18.59","v3.16.44","v4.9.34","v4.4.74","v3.18.58","v4.4.73","v3.18.57","v4.1.41","v4.9.33","v4.9.32","v4.4.72","v4.9.31","v4.4.71","v3.18.56","v4.1.40","v4.9.30","v4.4.70","v3.18.55","v3.16.43","v4.9.29","v4.4.69","v3.18.54","v4.9.28","v4.4.68","v3.18.53","v4.1.39","v3.18.52","v4.9.27","v4.4.67","v4.9.26","v4.4.66","v3.18.51","v4.9.25","v4.4.65","v4.4.64","v3.18.50","v4.9.24","v4.4.63","v3.18.49","v4.9.23","v4.4.62","v3.18.48","v4.4.61","v4.9.22","v4.9.21","v4.4.60","v4.4.59","v4.9.20","v3.16.42","v4.9.19","v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