# CVE-2026-68429: drm/dp_mst: Handle torn-down topology gracefully in drm_dp_mst_topology_queue_probe()

Status: published. Published: 2026-08-12. Updated: 2026-11-06.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 5f57a96e92c60f62da91d58ceb5e5acd40e7d594; < b1d05cc61dfa6c4bd5e67855bec6a03e955f512d (affected, git); ≥ dbaeef363ea54f4c18112874b77503c72ba60fec; < 4ed6d08c4a59ee6a8cb806347f6d9873de5d229e (affected, git); ≥ dbaeef363ea54f4c18112874b77503c72ba60fec; < 8c6d84a54823cd839e6ce22af559925f1320c310 (affected, git); ≥ dbaeef363ea54f4c18112874b77503c72ba60fec; < afdff9103818656627920c21822e48a6dae2906f (affected, git); ≥ dbaeef363ea54f4c18112874b77503c72ba60fec; < 613059875958e7b217b250ed14c3b189f9488421 (affected, git); ≥ 6.6.86; < 6.6.148 (affected, semver). Source: CNA: Linux
- Linux / Linux: 6.12 (affected); ≥ 0; < 6.12 (unaffected, semver); ≥ 6.6.148; ≤ 6.6.* (unaffected, semver); ≥ 6.12.101; ≤ 6.12.* (unaffected, semver); ≥ 6.18.42; ≤ 6.18.* (unaffected, semver); ≥ 7.1.6; ≤ 7.1.* (unaffected, semver); ≥ 7.2; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.17% as of 2026-11-06; percentile 6.24%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/b1d05cc61dfa6c4bd5e67855bec6a03e955f512d (CNA: Linux)

- https://git.kernel.org/stable/c/4ed6d08c4a59ee6a8cb806347f6d9873de5d229e (CNA: Linux)

- https://git.kernel.org/stable/c/8c6d84a54823cd839e6ce22af559925f1320c310 (CNA: Linux)

- https://git.kernel.org/stable/c/afdff9103818656627920c21822e48a6dae2906f (CNA: Linux)

- https://git.kernel.org/stable/c/613059875958e7b217b250ed14c3b189f9488421 (CNA: Linux)

- https://git.kernel.org/stable/c/4ed6d08c4a59ee6a8cb806347f6d9873de5d229e (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/613059875958e7b217b250ed14c3b189f9488421 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/8c6d84a54823cd839e6ce22af559925f1320c310 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/afdff9103818656627920c21822e48a6dae2906f (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/b1d05cc61dfa6c4bd5e67855bec6a03e955f512d (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-68429; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68429; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-68429; retrieved 2026-11-06; source updated Not reported

Revision: b66a7867967b7fa09eab7295585ee4fc6ec0a9b7f7b9e53c86c072dd2896ae34

Canonical: https://y2.dev/cve/CVE-2026-68429

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