CVE-2026-74535 Bluetooth: ISO: avoid deadlocks in iso_sock_timeout
A use-after-free vulnerability in the Linux kernel's Bluetooth ISO subsystem allows attackers to cause a denial of service or potentially execute code via concurrent operations.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74535?
CVE-2026-74535 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: ISO: avoid deadlocks in iso_sock_timeout
iso_sock_timeout() takes lock_sock, so sync disabling the timer while holding that lock may deadlock.
iso_sock_timeout() may also run concurrently with iso_conn_del(), which leads to UAF
[Task 1] [Task hdev->workqueue] iso_sock_timeout iso_conn_del iso_conn_hold_unless_zero iso_chan_del `------------> iso_conn_put caller frees hcon iso_conn_put iso_conn_free conn->hcon->iso_data = NULL; /* UAF */
Fix the deadlock by removing the disable from the lock_sock sections. Move the timer from iso_conn to iso_pinfo to decouple it from iso_conn which may need to be freed in lock_sock section. Convert some of the clear_timer to disable_timer.
Which versions are affected by CVE-2026-74535?
How do I fix CVE-2026-74535?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-74535 being exploited?
There is no known exploitation of CVE-2026-74535 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74535, DEBIAN-CVE-2026-74535, GHSA-m6r7-j582-3j5f, UBUNTU-CVE-2026-74535.