net/tcp-ao: fix use-after-free of current_key on reconnect to another peer

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80849
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-04 16:18:13 UTC
Updated2026-09-04 16:18:13 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: net/tcp-ao: fix use-after-free of current_key on reconnect to another peer tcp_inbound_ao_hash() is called before bh_lock_sock_nested() is taken, with only rcu_read_lock() held. On the fast path for established sockets, if the rnext_keyid sent by the peer differs from current_key->sndid, the key the peer asked for is looked up and stored in current_key. The lookup is inside the RCU read side, but current_key outlives it. When the socket is disconnected and connect() is called again for another peer, tcp_ao_connect_init() unlinks every key that does not match the new peer and frees it with call_rcu(). If current_key points at such a key, it is cleared to NULL. The fast path reads sk_state only once on entry, so a softirq that got into it while the socket was still established can update current_key after that loop has already run. The update is inside the RCU read side, so it comes before the call_rcu() callback, and once the callback frees the key, current_key is left pointing at freed memory. The next transmission picks that pointer up in tcp_get_current_key(). tcp_ao_transmit_skb() then reads the traffic key from the freed object, which is the use-after-free. Wait for one grace period before unlinking, and only if a key is going to be removed. By the time tcp_connect() runs the socket is already in TCP_SYN_SENT, and TCP_AO_ESTABLISHED does not contain TCPF_SYN_SENT, so a softirq entering after the wait cannot reach the fast path, and the ones already in it have finished. The existing NULL handling in the loop is then enough.

Risk And Classification

EPSS: 0.001680000 probability, percentile 0.063360000 (date 2026-09-07)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 0a3a809089eb1d4a0a2fd0c16b520d603988c859 84a93b4e012587d0a4a84ffb23ec6da18e9d85f9 git Not specified
CNA Linux Linux affected 0a3a809089eb1d4a0a2fd0c16b520d603988c859 73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3 git Not specified
CNA Linux Linux affected 0a3a809089eb1d4a0a2fd0c16b520d603988c859 e54ad693eddb40c595add013f545354c538e325b git Not specified
CNA Linux Linux affected 0a3a809089eb1d4a0a2fd0c16b520d603988c859 2857dcbd03cf3354af0fba1b65c6a260fb43811a git Not specified
CNA Linux Linux affected 0a3a809089eb1d4a0a2fd0c16b520d603988c859 da4471557f279d0f56605158a625bb6e49ef7d41 git Not specified
CNA Linux Linux affected 6.7 Not specified
CNA Linux Linux unaffected 6.7 semver Not specified
CNA Linux Linux unaffected 6.12.108 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.49 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.13 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2.3 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/e54ad693eddb40c595add013f545354c538e325b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2857dcbd03cf3354af0fba1b65c6a260fb43811a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/84a93b4e012587d0a4a84ffb23ec6da18e9d85f9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/da4471557f279d0f56605158a625bb6e49ef7d41 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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