CVE-2026-72389 bridge: stp: Fix a potential use-after-free when deleting a bridge
A missing check in Linux kernel bridge STP timers allows a use-after-free when deleting a bridge, potentially leading to code execution or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72389?
CVE-2026-72389 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:
bridge: stp: Fix a potential use-after-free when deleting a bridge
The three STP timers are not supposed to be armed while the bridge is administratively down. They are synchronously deactivated when the bridge is put administratively down and the various call sites check for 'IFF_UP' before arming them.
This check is missing from br_topology_change_detection() and it is possible to engineer a situation in which the topology change timer is armed while the bridge is administratively down, resulting in a use-after-free [1] when the bridge is deleted.
Fix by adding the missing check and for good measures synchronously shutdown the three timers when the bridge is deleted.
[1] ODEBUG: free active (active state 0) object: ffff88811662b9b0 object type: timer_list hint: br_topology_change_timer_expired (net/bridge/br_stp_timer.c:120) WARNING: lib/debugobjects.c:629 at debug_print_object+0x1bc/0x450, CPU#9: ip/359
Which versions are affected by CVE-2026-72389?
How do I fix CVE-2026-72389?
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-2026-72389 being exploited?
There is no known exploitation of CVE-2026-72389 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72389, DEBIAN-CVE-2026-72389, GHSA-7jq5-5rp7-v6gf, UBUNTU-CVE-2026-72389.