CVE-2026-63856

A flaw was found in the Linux kernel's AMDGPU Video Core Next (VCN) 2.0 component. This vulnerability arises because the VCN encoder and decoder rings do not properly support 64-bit user fence writes. An attacker could exploit this by submitting command sequences with 64-bit user fences, leading to the rejection of these submissions and a denial of service for affected applications.

This vulnerability is evaluated as Moderate severity because successful exploitation requires local user access with rights to interact with GPU device nodes, and the impact is confined to a denial of service without compromising system confidentiality or integrity. Deployments without AMD graphics hardware or systems not utilizing Video Core Next 2.0 video processing capabilities are unaffected. In typical enterprise server environments where direct GPU rendering interfaces are not exposed to untrusted users, risk exposure is minimal.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.