---
id: CVE-2026-74489
title: 'wifi: mac80211: fix tid_tx use-after-free on BA session stop'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  wifi: mac80211: fix tid_tx use-after-free on BA session stop

  ieee80211_stop_tx_ba_cb() hands tid_tx to kfree_rcu() through
  ieee80211_remove_tid_tx(), and then reads ti…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 98acd4c1d9f7dc9c426e840c16e81b57315ff84b <
    09fc36eec7841cdf732f4db39855e0c73bd075cc
  - >-
    Linux >= 98acd4c1d9f7dc9c426e840c16e81b57315ff84b <
    2f067f5a450ea07efd249142a11d940a068fe29c
  - Linux 7.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T18:58:01.786843Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T19:05:49.622Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-74489'
references:
  - url: 'https://git.kernel.org/stable/c/09fc36eec7841cdf732f4db39855e0c73bd075cc'
  - url: 'https://git.kernel.org/stable/c/2f067f5a450ea07efd249142a11d940a068fe29c'
tags:
  - cve.org
epss: 0.0034
epssPercentile: 0.25942
ingestedAt: '2026-10-16T19:46:24.359Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

wifi: mac80211: fix tid_tx use-after-free on BA session stop

ieee80211_stop_tx_ba_cb() hands tid_tx to kfree_rcu() through
ieee80211_remove_tid_tx(), and then reads tid_tx->ndp after dropping
sta->lock:

	ieee80211_remove_tid_tx(sta, tid);	/* kfree_rcu(tid_tx, rcu_head) */
	...
	spin_unlock_bh(&sta->lock);

	if (start_txq)
		ieee80211_agg_start_txq(sta, tid, false);

	if (send_delba)
		ieee80211_send_delba(..., tid_tx->ndp);

That read is not covered by an RCU read-side critical section, and it runs
in preemptible process context: both callers hold the wiphy mutex, reaching
it either from the ieee80211_ba_session_work() wiphy work or from
ieee80211_sta_tear_down_BA_sessions() during station teardown.
Softirqs can run in that window too, both from the local_bh_enable() that
ends ieee80211_agg_start_txq() and from any interrupt exit, so the RCU
callback can free tid_tx before the read.

Driving the function from a test module with the grace period forced into
that window, KASAN reports the read, and the free arrives on the ordinary
RCU softirq path:

  BUG: KASAN: slab-use-after-free in ieee80211_stop_tx_ba_cb+0x3cd/0x400
  Read of size 1 at addr ffff888002b9f52e by task kworker/0:1/10
  [...]
  Freed by task 57:
   __kasan_slab_free+0x47/0x70
   __rcu_free_sheaf_prepare+0x70/0x250
   rcu_free_sheaf_nobarn+0x18/0x40
   rcu_core+0x426/0x1310
   handle_softirqs+0x144/0x590
   __irq_exit_rcu+0xea/0x150
   irq_exit_rcu+0x9/0x20
   sysvec_apic_timer_interrupt+0x6b/0x80
   asm_sysvec_apic_timer_interrupt+0x1a/0x20

send_delba is only set when tx_stop is set, which happens for
AGG_STOP_LOCAL_REQUEST alone, so this is reached on local teardown -
session idle timeout, PTK rekey, suspend, HW reconfig - and not from a
peer's DELBA.

Read ndp into a local before the session is freed, while sta->lock is still
held. tid_tx->ndp has a single writer, in
ieee80211_tx_ba_session_handle_start(), which cannot run concurrently here:
both paths are serialised by the wiphy mutex, and the session is already
marked HT_AGG_STATE_STOPPING at this point. tid_tx->ndp is also the only
tid_tx dereference left after ieee80211_remove_tid_tx() in this function.

[move/change the comment a bit to be more general not just on ndp,
 initialize ndp directly]

## Affected

- `Linux >= 98acd4c1d9f7dc9c426e840c16e81b57315ff84b < 09fc36eec7841cdf732f4db39855e0c73bd075cc`
- `Linux >= 98acd4c1d9f7dc9c426e840c16e81b57315ff84b < 2f067f5a450ea07efd249142a11d940a068fe29c`
- `Linux 7.1`

## Remediation

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