CVE-2025-21819 is a vulnerability identified in the Linux kernel related to the AMD display driver subsystem, specifically concerning the handling of Panel Self Refresh (PSR) version 1 functionality. The issue arises from the commit a2b5a9956269, which introduced the use of a hardware lock manager for PSR1 in the drm/amd/display driver. This change was later reverted due to the discovery that it could cause the system to hang when connecting two embedded DisplayPort (eDP) panels simultaneously. The vulnerability manifests as a potential system hang or freeze, which impacts system availability. The root cause appears to be a concurrency or resource management flaw in the hardware lock handling for PSR1, leading to deadlock or livelock conditions when multiple eDP panels are connected. The affected Linux kernel versions include several specific commits identified by their hashes, indicating that the issue is present in certain recent kernel builds prior to the reversion. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability does not appear to directly compromise confidentiality or integrity but can cause denial of service through system hangs. The problem is specific to systems using AMD graphics hardware with dual eDP panel configurations, which are common in some laptops and embedded systems. The fix involves reverting the problematic commit to restore previous lock management behavior, preventing the hang condition.

For European organizations, the primary impact of CVE-2025-21819 is on system availability, particularly for devices running Linux kernels with the affected AMD display driver versions and using dual eDP panel setups. This could affect laptops, workstations, or embedded devices in sectors such as manufacturing, research, and government where AMD hardware and Linux are prevalent. System hangs can disrupt business operations, cause data loss if unsaved work is interrupted, and increase support and maintenance costs. Critical infrastructure or industrial control systems using such hardware could experience operational downtime, potentially affecting service delivery. Although no direct data breach or integrity compromise is indicated, the denial-of-service nature of this vulnerability can be exploited to degrade system reliability. European organizations relying on Linux-based AMD hardware should be aware of this risk, especially those with remote or unattended systems where manual recovery from hangs is difficult. The absence of known exploits reduces immediate risk, but the vulnerability should be addressed proactively to avoid potential future exploitation or operational disruptions.

1. Apply the official Linux kernel patches that revert the problematic commit a2b5a9956269 as soon as they are available from trusted Linux distribution vendors or the Linux kernel maintainers. 2. For organizations compiling their own kernels, ensure to exclude or revert the specific commit causing the issue. 3. Identify and inventory systems using AMD graphics hardware with dual eDP panel configurations to prioritize patching. 4. Implement monitoring to detect system hangs or unresponsive states that may indicate triggering of this vulnerability. 5. Where possible, avoid configurations with multiple eDP panels until patches are applied. 6. Maintain regular backups and implement automated recovery procedures to minimize downtime impact from unexpected system hangs. 7. Engage with hardware vendors and Linux distribution support channels for guidance on updates and workarounds. 8. Test patches in controlled environments before wide deployment to ensure stability and compatibility. 9. Educate IT support teams about the symptoms and recovery steps related to this vulnerability to reduce incident response time.