{"id":"CVE-2026-80849","summary":"net/tcp-ao: fix use-after-free of current_key on reconnect to another peer","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.","modified":"2026-09-06T03:46:27.815828746Z","published":"2026-09-04T15:54:59.412Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80849.json","cna_assigner":"Linux"},"references":[{"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"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80849.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80849"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0a3a809089eb1d4a0a2fd0c16b520d603988c859"},{"fixed":"84a93b4e012587d0a4a84ffb23ec6da18e9d85f9"},{"fixed":"73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3"},{"fixed":"e54ad693eddb40c595add013f545354c538e325b"},{"fixed":"2857dcbd03cf3354af0fba1b65c6a260fb43811a"},{"fixed":"da4471557f279d0f56605158a625bb6e49ef7d41"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80849.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.108"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.49"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.13"}]},{"type":"ECOSYSTEM","events":[{"introduced":"7.2.0"},{"fixed":"7.2.3"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80849.json"}}],"schema_version":"1.9.0"}