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

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-19 · updated 2026-08-17
Weakness: CWE-416

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.

Affected products

Linux kernel: from 6.7 before 6.12.95; from 6.13 before 6.18.38; from 6.19 before 7.1.3 — fixed in 6.12.95, 6.18.38, 7.1.3

How to fix

Upgrade to a fixed version: Linux kernel 6.12.95, 6.18.38, 7.1.3. Check the vendor advisory for mitigations.

References

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