Linux Kernel: CFM Peer MEP Deletion Race (CVE-2026-23393)
CVE-2026-23393 Published on March 25, 2026
bridge: cfm: Fix race condition in peer_mep deletion
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.
Products Associated with CVE-2026-23393
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Affected Versions
Linux:- Version dc32cbb3dbd7da38c700d6e0fc6354df24920525 and below e89dbd2736a45f0507949af4748cbbf3ff793146 is affected.
- Version dc32cbb3dbd7da38c700d6e0fc6354df24920525 and below d8f35767bacb3c7769d470a41cf161e3f3c07e70 is affected.
- Version dc32cbb3dbd7da38c700d6e0fc6354df24920525 and below 1fd81151f65927fd9edb8ecd12ad45527dbbe5ab is affected.
- Version dc32cbb3dbd7da38c700d6e0fc6354df24920525 and below 3715a00855316066cdda69d43648336367422127 is affected.
- Version 5.11 is affected.
- Before 5.11 is unaffected.
- Version 6.12.78, <= 6.12.* is unaffected.
- Version 6.18.20, <= 6.18.* is unaffected.
- Version 6.19.10, <= 6.19.* is unaffected.
- Version 7.0-rc5, <= * is unaffected.