{"id":"AZL-94476","summary":"CVE-2026-64581 affecting package kernel 6.6.150.1-1","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":"2026-08-29T05:27:27Z","published":"2026-08-05T08:16:38Z","upstream":["CVE-2026-64581"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64581"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.150.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-94476.json"}}],"schema_version":"1.9.0"}