Bug 2502221 (CVE-2026-53389)

Summary: CVE-2026-53389 kernel: net/tcp-ao: fix use-after-free of key in del_async path
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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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.
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Description OSIDB Bzimport 2026-07-19 13:02:34 UTC 
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.
Comment 1 Keith Grant 2026-07-20 13:44:32 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071955-CVE-2026-53389-36cb@gregkh/T