CVE-2025-37967 in Linux
Summary
by MITRE • 05/20/2025
In the Linux kernel, the following vulnerability has been resolved:
usb: typec: ucsi: displayport: Fix deadlock
This patch introduces the ucsi_con_mutex_lock / ucsi_con_mutex_unlock functions to the UCSI driver. ucsi_con_mutex_lock ensures the connector mutex is only locked if a connection is established and the partner pointer is valid. This resolves a deadlock scenario where ucsi_displayport_remove_partner holds con->mutex waiting for dp_altmode_work to complete while dp_altmode_work attempts to acquire it.
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Analysis
by VulDB Data Team • 12/16/2025
The vulnerability CVE-2025-37967 addresses a critical deadlock condition within the Linux kernel's USB Type-C subsystem, specifically within the UCSI (USB Type-C System Controller Interface) driver implementation. This issue manifests in the displayport altmode handling functionality where concurrent operations create a circular dependency that halts system progress. The UCSI driver serves as a bridge between the USB Type-C controller and the system's USB subsystem, managing the complex negotiation and configuration of USB Type-C connections including alternate modes such as DisplayPort. The vulnerability arises from improper mutex handling during the removal of DisplayPort partner devices, creating a scenario where system threads become indefinitely blocked.
The technical flaw stems from a race condition in the ucsi_displayport_remove_partner function which attempts to acquire a mutex while another thread holds the same mutex in the dp_altmode_work function. This creates a classic deadlock scenario where each thread waits for the other to release the lock it needs, effectively freezing the USB Type-C subsystem. The patch implements a new locking mechanism through ucsi_con_mutex_lock and ucsi_con_mutex_unlock functions that introduce a conditional locking approach. These functions ensure that the connector mutex is only acquired when a valid connection exists and the partner pointer is properly established, preventing the acquisition of locks on invalid or disconnected hardware states.
The operational impact of this vulnerability extends beyond simple system freezing, potentially affecting device connectivity and system stability in environments where USB Type-C devices are frequently connected and disconnected. Systems relying heavily on USB Type-C for display outputs, external storage, or power delivery could experience complete loss of USB Type-C functionality until a system reboot occurs. This affects desktop computers, laptops, and embedded systems that utilize the UCSI driver for USB Type-C management, particularly those supporting DisplayPort alternate modes. The vulnerability is especially concerning in enterprise environments where USB Type-C hubs and docking stations are commonly used, as it could lead to widespread connectivity issues and service disruptions.
Mitigation strategies involve applying the kernel patch that implements the conditional mutex locking mechanism, ensuring that all affected systems receive the security update through standard distribution channels. Organizations should prioritize deployment of this patch across all systems running affected kernel versions, particularly those with high USB Type-C usage. System administrators should monitor for potential deadlocks during device connection and disconnection events, as the vulnerability may manifest under specific timing conditions. The fix aligns with security best practices for concurrent programming and follows the principle of least privilege in mutex acquisition, preventing unnecessary lock acquisitions that could lead to system-level blocking conditions. This vulnerability demonstrates the importance of proper synchronization mechanisms in kernel drivers and highlights the need for comprehensive testing of concurrent operations in USB subsystems. The issue relates to CWE-362, which addresses race conditions, and could potentially map to ATT&CK technique T1547.001 for privilege escalation through kernel-level vulnerabilities that affect system stability and availability.