---
id: CVE-2026-80849
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_lo…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 <
    84a93b4e012587d0a4a84ffb23ec6da18e9d85f9
  - >-
    Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 <
    73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3
  - >-
    Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 <
    e54ad693eddb40c595add013f545354c538e325b
  - >-
    Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 <
    2857dcbd03cf3354af0fba1b65c6a260fb43811a
  - >-
    Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 <
    da4471557f279d0f56605158a625bb6e49ef7d41
  - Linux 6.7
published: '2026-09-04'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T08:44:43.405Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-80849'
references:
  - url: 'https://git.kernel.org/stable/c/84a93b4e012587d0a4a84ffb23ec6da18e9d85f9'
  - url: 'https://git.kernel.org/stable/c/73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3'
  - url: 'https://git.kernel.org/stable/c/e54ad693eddb40c595add013f545354c538e325b'
  - url: 'https://git.kernel.org/stable/c/2857dcbd03cf3354af0fba1b65c6a260fb43811a'
  - url: 'https://git.kernel.org/stable/c/da4471557f279d0f56605158a625bb6e49ef7d41'
tags:
  - cve.org
epss: 0.00168
epssPercentile: 0.05678
ingestedAt: '2026-10-19T09:16:01.495Z'
---

## Overview

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.

## Affected

- `Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 < 84a93b4e012587d0a4a84ffb23ec6da18e9d85f9`
- `Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 < 73fde8fe4469f4ed8f0afcc0b9d6413002a9e6b3`
- `Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 < e54ad693eddb40c595add013f545354c538e325b`
- `Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 < 2857dcbd03cf3354af0fba1b65c6a260fb43811a`
- `Linux >= 0a3a809089eb1d4a0a2fd0c16b520d603988c859 < da4471557f279d0f56605158a625bb6e49ef7d41`
- `Linux 6.7`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.