CVE-2025-37870 is a vulnerability identified in the Linux kernel specifically within the Direct Rendering Manager (DRM) subsystem for AMD display drivers. The flaw arises during the link training phase of the display interface, where the physical (phy) clock is disabled if link training fails. However, the kernel's enable_streams function incorrectly assumes that link training has succeeded and attempts to select the phy clock via a multiplexer. This results in a system hang when a register write is performed to the disabled phy clock. The root cause is a lack of proper validation of the link training status before enabling the stream. The fix involves modifying enable_stream to detect a failed link training state and fallback to using the reference clock instead of the phy clock, thereby preventing the hang and maintaining system recoverability. This vulnerability affects Linux kernel versions identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and was publicly disclosed in May 2025. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, this vulnerability could lead to system instability or denial of service (DoS) conditions on Linux systems using AMD graphics hardware with the affected kernel versions. The hang occurs during display initialization or mode setting, potentially impacting workstations, servers, or embedded devices relying on AMD GPUs for graphical output. This could disrupt critical operations, especially in environments where Linux is used for graphical workloads, such as design, media, or scientific computing. While the vulnerability does not appear to allow privilege escalation or code execution, the resulting system hang could cause operational downtime, data loss if unsaved work is interrupted, and increased support costs. Organizations with large Linux deployments or those using AMD GPUs in critical infrastructure should be particularly cautious. Since no known exploits exist yet, the immediate risk is moderate, but the potential for future exploitation remains if attackers develop techniques to trigger the hang remotely or via user interaction.

Organizations should promptly update their Linux kernels to versions that include the patch addressing CVE-2025-37870. Specifically, they should track kernel releases incorporating the fix that adds the fallback to the reference clock when link training fails. For environments where immediate patching is not feasible, administrators can consider disabling AMD GPU usage or switching to alternative graphics drivers if possible to avoid triggering the vulnerable code path. Monitoring system logs for repeated display initialization failures or hangs can help detect attempts to exploit this issue. Additionally, implementing robust system monitoring and automated recovery mechanisms (such as watchdog timers or automated reboots) can reduce downtime caused by unexpected hangs. Testing updates in staging environments before deployment is recommended to ensure compatibility and stability. Finally, maintaining up-to-date inventory of Linux kernel versions and AMD hardware in use will facilitate targeted mitigation efforts.