CVE-2026-68429 drm/dp_mst: Handle torn-down topology gracefully in drm_dp_mst_topology_queue_probe()
A race condition in the Linux kernel DP MST driver causes compositor crashes when connecting or disconnecting monitors, requiring local physical access.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-68429?
CVE-2026-68429 is a vulnerability in Linux, published on 12 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
In the Linux kernel, the following vulnerability has been resolved:
drm/dp_mst: Handle torn-down topology gracefully in drm_dp_mst_topology_queue_probe()
A hotplug or link-loss event can tear down the MST topology (setting mgr->mst_state = false and mgr->mst_primary = NULL) concurrently with a caller invoking drm_dp_mst_topology_queue_probe(). Since the check is already performed under mgr->lock, the condition is not a programming error but a valid race -- the topology was valid when the caller decided to call this function, but was torn down before the lock was acquired.
Replace the drm_WARN_ON() with a graceful early return. This eliminates spurious kernel warnings and the resulting compositor crashes observed when connecting/disconnecting DP MST monitors, while keeping the correct behavior of doing nothing when MST is not active. A drm_dbg_mst() trace is added so the skipped probe remains observable under MST debug logging.
The existing WARN_ON(mgr->mst_primary) in drm_dp_mst_topology_mgr_set_mst() already catches the case where the topology is initialized twice, so no diagnostic coverage is lost.
Which versions are affected by CVE-2026-68429?
How do I fix CVE-2026-68429?
Apply the vendor's patch.
Is CVE-2026-68429 being exploited?
There is no known exploitation of CVE-2026-68429 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68429, DEBIAN-CVE-2026-68429, GHSA-47qh-xgqx-2fv5, UBUNTU-CVE-2026-68429.