CVE-2026-89773: Linux Kernel Display Driver HDCP Vulnerability

CVE-2026-89773 Overview

CVE-2026-89773 affects the Linux kernel's AMD display driver (drm/amd/display). The vulnerability involves the High-bandwidth Digital Content Protection (HDCP) configuration routine being invoked during a transition state that lacks a valid dm_stream_ctx structure. The HDCP routine should execute only when a valid stream has been created. Executing the routine without a valid stream context can lead to unstable driver behavior in the Direct Rendering Manager (DRM) subsystem. Upstream maintainers have resolved the issue by skipping HDCP configuration updates during transition states.

Critical Impact
Invoking the HDCP configuration routine without a valid dm_stream_ctx can produce invalid memory references inside the AMD display driver, affecting kernel stability on affected systems.

Affected Products

Linux kernel with AMD display driver (drm/amd/display)
Systems using AMD GPUs with HDCP-capable outputs
Distributions shipping the affected upstream kernel commits

Discovery Timeline

2026-09-11 - CVE-2026-89773 published to NVD
2026-09-13 - Last updated in NVD database

Technical Details for CVE-2026-89773

Vulnerability Analysis

The flaw resides in the AMD display driver component of the Linux kernel, specifically in the HDCP update path. During display pipeline reconfiguration, the driver can enter a transition state where the dm_stream_ctx structure is not yet initialized or has already been torn down. The HDCP configuration routine assumes a valid stream context exists and proceeds to reference stream-dependent state. This premature execution creates a window where the driver operates on incomplete or invalid data structures.

The fix, delivered in kernel commits d5164580 and f733276a, adds a guard that skips the HDCP configuration update when the driver is in a transition state without a valid stream. The routine now runs only when a valid stream has been created, aligning behavior with the intended state machine.

Root Cause

The root cause is missing state validation in the HDCP update path within the AMD display driver. The code did not verify that dm_stream_ctx was valid before proceeding with HDCP configuration during stream transitions. This is a classic state-handling defect where an operation is performed outside its valid lifecycle window.

Attack Vector

No remote or authenticated attack vector has been documented. The issue is a driver-level state-handling defect triggered during display pipeline transitions. See the upstream commits for technical details: Kernel Git Commit d5164580 and Kernel Git Commit f733276a.

Detection Methods for CVE-2026-89773

Indicators of Compromise

Kernel log messages referencing amdgpu, drm, or HDCP faults during display mode changes
Unexpected display driver warnings or oops entries in dmesg around HDCP-protected output transitions
System instability correlated with hotplug or display reconfiguration events on AMD GPUs

Detection Strategies

Inventory Linux hosts running kernel versions predating the upstream commits d5164580 and f733276a
Compare running kernel version (uname -r) against distribution advisories referencing CVE-2026-89773
Monitor kernel crash reports and journal entries for AMD display driver traces during HDCP negotiation

Monitoring Recommendations

Collect and centralize dmesg and journalctl -k output from AMD GPU workstations for review
Alert on repeated AMD display driver warnings or kernel panics referencing HDCP paths
Track kernel package versions across the fleet to confirm patch adoption

How to Mitigate CVE-2026-89773

Immediate Actions Required

Identify systems running affected Linux kernel versions with the AMD display driver
Apply the vendor-supplied kernel update that includes commits d5164580 and f733276a
Reboot patched systems to activate the corrected kernel image

Patch Information

The fix is available in the upstream Linux kernel stable tree via Kernel Git Commit d5164580 and Kernel Git Commit f733276a. Users should install the kernel package containing these commits through their distribution's update channel.

Workarounds

No official workaround has been published; applying the upstream patch is the recommended remediation
Where patching is delayed, avoid frequent display mode changes on HDCP-protected outputs to reduce exposure to the transition-state path

bash

# Verify current kernel version and update through the distribution package manager
uname -r

# Debian / Ubuntu
sudo apt update && sudo apt upgrade linux-image-generic

# RHEL / Fedora
sudo dnf update kernel

# Reboot to load the patched kernel
sudo reboot