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

{
  "id": "05b25072ef12db08207ecc7529874605c2e70144cfe0f073e0da186f36934f63",
  "url": "https://osv.dev/vulnerability/CVE-2026-80849",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "net/tcp-ao: fix use-after-free of current_key on reconnect to another peer",
    "summary": "In 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 cann",
    "evidence": "osv:CVE-2026-80849",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.108",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.49",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.13",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.3",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-80849",
      "aliases": [
        "CVE-2026-80849"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "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"
          }
        },
        {
          "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"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80849.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:29.707367114Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/2857dcbd03cf3354af0fba1b65c6a260fb43811a",
        "https://git.kernel.org/stable/c/73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3",
        "https://git.kernel.org/stable/c/84a93b4e012587d0a4a84ffb23ec6da18e9d85f9",
        "https://git.kernel.org/stable/c/da4471557f279d0f56605158a625bb6e49ef7d41",
        "https://git.kernel.org/stable/c/e54ad693eddb40c595add013f545354c538e325b",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80849.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-80849",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80849.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-80849",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 496758,
  "published_at": "2026-09-04T15:54:59.412+00:00"
}