CVE-2025-37967

What it actually does

A deadlock occurs in the UCSI Type-C driver when ucsi_displayport_remove_partner holds the connector mutex waiting for dp_altmode_work to complete while the work item simultaneously attempts to acquire the same mutex; the patch adds ucsi_con_mutex_lock/unlock helpers that only lock when a valid partner connection exists.

Why it matters to the business

Linux systems using USB Type-C with DisplayPort alt mode can experience kernel-level hangs requiring reboots, leading to downtime and operational disruption across numerous Ubuntu LTS releases and their downstream dependents.

How an attack unfolds

An attacker with local access would attempt to trigger concurrent DisplayPort partner attach/remove events that race on the connector mutex, but the flaw is a stability issue with no public exploits or ransomware use and low EPSS; listed threat actors reference unrelated kernel privilege-escalation campaigns.

How to fix it

Upgrade affected packages to the listed fixed versions (e.g., linux 3.11.0-12.19 on Ubuntu 14.04, linux 4.4.0-2.16 on Ubuntu 16.04, linux 4.13.0-16.19 on Ubuntu 18.04, and corresponding -aws/-azure/-gcp/-hwe/-oracle variants) and reboot.

How to confirm the fix worked

Verify installed kernel versions match the fixed releases for each package; inspect UCSI driver source for presence of ucsi_con_mutex_lock/unlock wrappers; monitor for absence of hung-task reports involving dp_altmode_work.

Typical attack path

1. Establish a USB Type-C DisplayPort alt-mode connection
2. Trigger partner removal while dp_altmode_work is queued
3. Force the work item and remove_partner path to contend on con->mutex
4. Induce deadlock and system unresponsiveness

How to detect it

Search kernel logs and dmesg for hung-task warnings, workqueue stalls, or mutex contention messages referencing ucsi_displayport, dp_altmode_work, or typec connector operations; correlate with USB-C plug/unplug events.

What your security team should do

• Apply the exact fixed kernel versions for all listed Ubuntu packages within the next maintenance window
• Test USB Type-C DisplayPort functionality post-upgrade on representative hardware
• Review kernel logs for prior hung-task or mutex deadlock signatures on affected systems
• Prioritize systems exposed to external USB-C peripherals given the 526 days since publication