CVE-2026-23393 bridge: cfm: Fix race condition in peer_mep deletion
A race condition in the Linux kernel bridge CFM module allows use-after-free, 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-2026-23393?
CVE-2026-23393 is a high-severity vulnerability in Linux kernel, published on 25 Mar 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: cfm: Fix race condition in peer_mep deletion
When a peer MEP is being deleted, cancel_delayed_work_sync() is called on ccm_rx_dwork before freeing. However, br_cfm_frame_rx() runs in softirq context under rcu_read_lock (without RTNL) and can re-schedule ccm_rx_dwork via ccm_rx_timer_start() between cancel_delayed_work_sync() returning and kfree_rcu() being called.
The following is a simple race scenario:
cpu0 cpu1
mep_delete_implementation() cancel_delayed_work_sync(ccm_rx_dwork); br_cfm_frame_rx() // peer_mep still in hlist if (peer_mep->ccm_defect) ccm_rx_timer_start() queue_delayed_work(ccm_rx_dwork) hlist_del_rcu(&peer_mep->head); kfree_rcu(peer_mep, rcu); ccm_rx_work_expired() // on freed peer_mep
To prevent this, cancel_delayed_work_sync() is replaced with disable_delayed_work_sync() in both peer MEP deletion paths, so that subsequent queue_delayed_work() calls from br_cfm_frame_rx() are silently rejected.
The cc_peer_disable() helper retains cancel_delayed_work_sync() because it is also used for the CC enable/disable toggle path where the work must remain re-schedulable.
Weakness: CWE-362
Which versions are affected by CVE-2026-23393?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23393?
Apply the vendor's patch.
Is CVE-2026-23393 being exploited?
There is no known exploitation of CVE-2026-23393 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-23393, DEBIAN-CVE-2026-23393, GHSA-27jv-r6jg-f5fr, ROOT-OS-DEBIAN-12-CVE-2026-23393, ROOT-OS-DEBIAN-13-CVE-2026-23393, ROOT-OS-UBUNTU-2204-CVE-2026-23393 and 2 more.