CVE-2026-53389: net/tcp-ao: fix use-after-free of key in del_async path

CVE-2026-53389: net/tcp-ao: fix use-after-free of key in del_async path

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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.

Clear current_key and rnext_key in the del_async path when they
reference the key being deleted.

The Linux kernel CVE team has assigned CVE-2026-53389 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.7 with commit d6732b95b6fbbc6d5bb9d2f809e275763640c4a2 and fixed in 6.12.95 with commit 6ce7ef41743740ce15c2061561b784148b565b3f
	Issue introduced in 6.7 with commit d6732b95b6fbbc6d5bb9d2f809e275763640c4a2 and fixed in 6.18.38 with commit e77fbefd1269b5c123e7c651a1ebdce1b87d19a0
	Issue introduced in 6.7 with commit d6732b95b6fbbc6d5bb9d2f809e275763640c4a2 and fixed in 7.1.3 with commit 7ddc29a094d96e9b3aa280433c6dc443df9eabf2
	Issue introduced in 6.7 with commit d6732b95b6fbbc6d5bb9d2f809e275763640c4a2 and fixed in 7.2-rc1 with commit 5ba9950bc9078e19b69cca1e56d1553b125c6857

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-53389
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/ipv4/tcp_ao.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/6ce7ef41743740ce15c2061561b784148b565b3f
	https://git.kernel.org/stable/c/e77fbefd1269b5c123e7c651a1ebdce1b87d19a0
	https://git.kernel.org/stable/c/7ddc29a094d96e9b3aa280433c6dc443df9eabf2
	https://git.kernel.org/stable/c/5ba9950bc9078e19b69cca1e56d1553b125c6857