GHSA-P98R-RJ2F-59M7
Vulnerability from github – Published: 2026-09-04 18:31 – Updated: 2026-09-04 18:31In 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.
{
"affected": [],
"aliases": [
"CVE-2026-80849"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-04T16:18:13Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/tcp-ao: fix use-after-free of current_key on reconnect to another peer\n\ntcp_inbound_ao_hash() is called before bh_lock_sock_nested() is taken,\nwith only rcu_read_lock() held. On the fast path for established\nsockets, if the rnext_keyid sent by the peer differs from\ncurrent_key-\u003esndid, the key the peer asked for is looked up and stored\nin current_key. The lookup is inside the RCU read side, but current_key\noutlives it.\n\nWhen the socket is disconnected and connect() is called again for\nanother peer, tcp_ao_connect_init() unlinks every key that does not\nmatch the new peer and frees it with call_rcu(). If current_key points\nat such a key, it is cleared to NULL.\n\nThe fast path reads sk_state only once on entry, so a softirq that got\ninto it while the socket was still established can update current_key\nafter that loop has already run. The update is inside the RCU read side,\nso it comes before the call_rcu() callback, and once the callback frees\nthe key, current_key is left pointing at freed memory.\n\nThe next transmission picks that pointer up in tcp_get_current_key().\ntcp_ao_transmit_skb() then reads the traffic key from the freed object,\nwhich is the use-after-free.\n\nWait for one grace period before unlinking, and only if a key is going\nto be removed. By the time tcp_connect() runs the socket is already in\nTCP_SYN_SENT, and TCP_AO_ESTABLISHED does not contain TCPF_SYN_SENT, so\na softirq entering after the wait cannot reach the fast path, and the\nones already in it have finished. The existing NULL handling in the loop\nis then enough.",
"id": "GHSA-p98r-rj2f-59m7",
"modified": "2026-09-04T18:31:29Z",
"published": "2026-09-04T18:31:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-80849"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2857dcbd03cf3354af0fba1b65c6a260fb43811a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/84a93b4e012587d0a4a84ffb23ec6da18e9d85f9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/da4471557f279d0f56605158a625bb6e49ef7d41"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e54ad693eddb40c595add013f545354c538e325b"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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Nomenclature
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