Advisory [CVE-2026-53389] fix use-after-free of key in del_async path

In the Linux kernel, the following vulnerability has been resolved: net/tcp-ao: fix use-after-free of key in del_async path In tcp_ao_delete_key(), the del_async path skips the current_key and rnext_key validity checks present in the synchronous path, assuming these pointers are always NULL on LISTEN sockets.

However, if a key was added with set_current=1/set_rnext=1 while the socket was in CLOSE state, current_key and rnext_key will be non-NULL after listen() transitions the socket to LISTEN. When such a key is deleted with del_async=1, hlist_del_rcu() and call_rcu() free the key without clearing the dangling pointers.

After the RCU grace period, getsockopt(TCP_AO_INFO) dereferences current_key->sndid and rnext_key->rcvid from freed slab memory. A flaw was found in the Linux kernel's TCP Authentication Option (TCP-AO) implementation.

When a TCP-AO key is deleted asynchronously, the system fails to clear pointers to the freed memory. This can allow an attacker to access previously freed memory, potentially leading to information disclosure or denial of service.

In some scenarios, this could also enable arbitrary code execution. Red Hat severity: not rated.

Weakness: CWE-825. Red Hat lists Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat Hardened Images as not affected.