CVE-2025-21956 drm/amd/display: Assign normalized_pix_clk when color depth = 14
A missing case in the AMD display driver causes a kernel warning and potential instability when using 14-bit color depth, requiring a patch.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-21956?
CVE-2025-21956 is a medium-severity denial of service vulnerability in Linux kernel, published on 1 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Assign normalized_pix_clk when color depth = 14
[WHY & HOW] A warning message "WARNING: CPU: 4 PID: 459 at ... /dc_resource.c:3397 calculate_phy_pix_clks+0xef/0x100 [amdgpu]" occurs because the display_color_depth == COLOR_DEPTH_141414 is not handled. This is observed in Radeon RX 6600 XT.
It is fixed by assigning pix_clk * (14 * 3) / 24 - same as the rests.
Also fixes the indentation in get_norm_pix_clk.
(cherry picked from commit 274a87eb389f58eddcbc5659ab0b180b37e92775)
Which versions are affected by CVE-2025-21956?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-21956?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-21956 being exploited?
There is no known exploitation of CVE-2025-21956 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-21956, DEBIAN-CVE-2025-21956, GHSA-mq3v-g8q8-f78r, ROOT-OS-UBUNTU-2404-CVE-2025-21956, UBUNTU-CVE-2025-21956.