CVE-2026-64572 is a vulnerability in Linux Kernel
Published on August 5, 2026
ipv4: fib: free fib_alias with kfree_rcu() on insert error path
In the Linux kernel, the following vulnerability has been resolved:
ipv4: fib: free fib_alias with kfree_rcu() on insert error path
fib_table_insert() publishes new_fa into the leaf's fa_list with
fib_insert_alias() before calling the fib entry notifiers. When a
notifier fails, the error path removes new_fa with fib_remove_alias()
(hlist_del_rcu) and frees it right away with kmem_cache_free().
fib_table_lookup() walks that list under rcu_read_lock() only, so a
concurrent lookup that already reached new_fa keeps reading it after the
free:
BUG: KASAN: slab-use-after-free in fib_table_lookup (net/ipv4/fib_trie.c:1601)
Read of size 1 at addr ffff88810676d4eb by task exploit/297
Call Trace:
fib_table_lookup (net/ipv4/fib_trie.c:1601)
ip_route_output_key_hash_rcu (net/ipv4/route.c:2814)
ip_route_output_key_hash (net/ipv4/route.c:2705)
__ip4_datagram_connect (net/ipv4/datagram.c:49)
udp_connect (net/ipv4/udp.c:2144)
__sys_connect (net/socket.c:2167)
__x64_sys_connect (net/socket.c:2173)
do_syscall_64
entry_SYSCALL_64_after_hwframe
which belongs to the cache ip_fib_alias of size 56
Triggering the error path needs CAP_NET_ADMIN and a registered fib
notifier that can reject a route; a netdevsim device whose IPv4 FIB
resource is exhausted is enough.
Free new_fa with alias_free_mem_rcu(), as fib_table_delete() already
does for a fib_alias removed from the trie.
Products Associated with CVE-2026-64572
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Affected Versions
Linux:- Version a6c76c17df021b141b0d306828c9fe4ba2d2717c and below 8150b5365f026e72250cacc527ea00be30f40105 is affected.
- Version a6c76c17df021b141b0d306828c9fe4ba2d2717c and below d007056868723de9c0cc3f5ffaad47a8d468b9a4 is affected.
- Version a6c76c17df021b141b0d306828c9fe4ba2d2717c and below cb8be318b4432abd88d3172ec157330f27a5f7a7 is affected.
- Version a6c76c17df021b141b0d306828c9fe4ba2d2717c and below b8d2ea75c76abcd0d72679c2f488271f573e32fb is affected.
- Version a6c76c17df021b141b0d306828c9fe4ba2d2717c and below f2f152e94a67bc746afaf05a1b2702c195553112 is affected.
- Version 5.6 is affected.
- Before 5.6 is unaffected.
- Version 6.6.148, <= 6.6.* is unaffected.
- Version 6.12.101, <= 6.12.* is unaffected.
- Version 6.18.42, <= 6.18.* is unaffected.
- Version 7.1.6, <= 7.1.* is unaffected.
- Version 7.2-rc4, <= * is unaffected.