CVE-2025-21956

Service interruption via unhandled 14-bit color depth

Published Apr 1, 2025 · Updated May 11, 2026

Improper pixel-clock calculation in the Linux kernel allows local users to interrupt service by selecting 14-bit display color depth. The get_norm_pix_clk path leaves normalized_pix_clk unset for COLOR_DEPTH_141414, so calculate_phy_pix_clks reaches a kernel warning instead of applying the required 14-bit scaling. Exploitation requires local low-privileged access and an AMD display configuration using 14-bit color; the documented impact is limited to availability.

CVSS severity5.5
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper pixel-clock calculation in the Linux kernel allows local users to interrupt service by selecting 14-bit display color depth. The get_norm_pix_clk path leaves normalized_pix_clk unset for COLOR_DEPTH_141414, so calculate_phy_pix_clks reaches a kernel warning instead of applying the required 14-bit scaling. Exploitation requires local low-privileged access and an AMD display configuration using 14-bit color; the documented impact is limited to availability.

The record

CVE
CVE-2025-21956
Published
Apr 1, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.15
  2. Affected versionversion=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <0174a2e5770efee9dbd4b58963ed4d939298ff5e
  3. Affected versionversion=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <04f90b505ad3a6eed474bbaa03167095fef5203a
  4. Affected versionversion=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <0c0016712e5dc23ce4a7e673cbebc24a535d8c8a
  5. Affected versionversion=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <27df30106690969f7d63604f0d49ed8e9bffa2cb
  6. Affected versionversion=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <79e31396fdd7037c503e6add15af7cb00633ea92
  7. Affected versionversion=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <a8f77e1658d78e4a8bb227a83bcee67de97f7634
  8. Affected versionversion=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <cca3ab74f90176099b6392e8e894b52b27b3d080
  9. Affected versionversion=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <dc831b38680c47d07e425871a9852109183895cf

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.15; version=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <0174a2e5770efee9dbd4b58963ed4d939298ff5e; version=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <04f90b505ad3a6eed474bbaa03167095fef5203a; version=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <0c0016712e5dc23ce4a7e673cbebc24a535d8c8a; version=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <27df30106690969f7d63604f0d49ed8e9bffa2cb; version=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <79e31396fdd7037c503e6add15af7cb00633ea92; version=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <a8f77e1658d78e4a8bb227a83bcee67de97f7634; version=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <cca3ab74f90176099b6392e8e894b52b27b3d080; version=4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c <dc831b38680c47d07e425871a9852109183895cf

Published CVSS scores

5.5CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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