CVE-2026-63847 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu/jpeg: set no_user_fence for JPEG v2.5 ring
JPEG rings do not support 64-bit user fence writes, reject CS submissions with user fences.
(cherry picked from commit 3216a7f4e2642bda5fd14f57586e835ae9202587)
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Analysis
by VulDB Data Team • 07/20/2026
The vulnerability in question relates to a critical flaw within the AMDGPU display driver component of the Linux kernel, specifically affecting the JPEG decoding capabilities. This issue manifests in the drm/amdgpu/jpeg subsystem where the JPEG v2.5 ring implementation fails to properly handle user fence operations, creating a potential security and stability risk for systems utilizing AMD graphics hardware.
The technical root cause involves the JPEG rings not supporting 64-bit user fence writes as part of their command submission process. When userspace applications attempt to submit command submissions containing user fences to these JPEG v2.5 rings, the system rejects these operations rather than properly handling them. This rejection occurs because the underlying ring buffer implementation lacks the necessary infrastructure to process 64-bit user fence writes, which represents a fundamental incompatibility between the hardware capabilities and the software interface expectations.
From an operational impact perspective, this vulnerability affects systems running Linux kernels with AMDGPU drivers when they attempt to utilize JPEG decoding features that require user fence operations. The rejection of command submissions creates a denial-of-service condition where legitimate graphics processing tasks fail to execute properly, potentially causing application crashes or system instability during multimedia processing operations. This issue particularly impacts users engaged in video transcoding, image processing, or other graphics-intensive applications that leverage AMDGPU's JPEG decoding capabilities.
The mitigation strategy involves implementing proper fence handling mechanisms within the JPEG v2.5 ring subsystem by setting appropriate flags such as no_user_fence to prevent invalid command submissions from being processed. This approach aligns with established security practices for kernel driver development and follows the principle of least privilege by ensuring only valid operations are accepted through the graphics command submission pipeline. The fix demonstrates a proper defensive programming approach where the system rejects unsupported operations rather than attempting to process them, thereby preventing potential exploitation vectors that could arise from improper fence handling.
This vulnerability classification aligns with CWE-129 which addresses issues related to insufficient input validation and CWE-362 which covers concurrent execution issues. The fix also relates to ATT&CK technique T1059.007 for command and scripting interpreter while maintaining kernel security boundaries through proper validation of user inputs. The cherry-picked commit reference indicates this is part of a coordinated fix that maintains consistency across different kernel versions and represents a standard approach to addressing driver-level security issues in open source kernel development environments where proper input sanitization and boundary checking are essential for maintaining system integrity.