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CVE Record

CVE-2025-21956: drm/amd/display: Assign normalized_pix_clk when color depth = 14

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)

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue affects AMD GPU display handling when a 14-bit color depth is used. The known symptom is a kernel warning, observed on Radeon RX 6600 XT. Sources do not provide CVSS, CWE, confirmed exploitation, or evidence of data compromise.

Executive priority

Treat this as low operational urgency unless the organization depends on AMD GPU Linux workstations or affected display workloads. Patch through normal kernel maintenance, with higher priority for fleets showing related kernel warnings.

Technical view

The amdgpu display code did not handle COLOR_DEPTH_141414 in pixel clock normalization. The fix assigns normalized_pix_clk using the same formula pattern as other depths: 14 bits across three channels over 24. The source describes a warning in calculate_phy_pix_clks and stable kernel fixes.

Likely exposure

Exposure is most likely on Linux systems using the AMDGPU display stack with affected kernel versions and AMD display hardware. The bundle lists Linux kernel impact and multiple stable branch fixes, plus Debian LTS advisories.

Exploitation context

CISA KEV status is false in the bundle, and no cited source claims active exploitation. The public description shows a reliability bug triggered by display color-depth handling, not a described remote or privilege-escalation path.

Researcher notes

Evidence is limited to the CVE description, stable kernel commits, and Debian LTS notices. No CVSS, CWE, exploit status, or broad impact claim is present. Avoid extrapolating beyond AMD display color-depth handling and kernel warning behavior.

Mitigation direction

  • Inventory Linux systems using AMD GPUs and the AMDGPU display stack.
  • Apply vendor kernel updates containing the referenced stable fixes.
  • Review Debian LTS advisories if using Debian long-term support kernels.
  • Track upstream or distribution guidance where packaged fixes are not yet available.

Validation and detection

  • Check installed kernel versions against vendor security advisories and stable fix availability.
  • Confirm AMDGPU-equipped systems receive updated kernel packages after patching.
  • Review kernel logs for recurring amdgpu display warnings after update.
  • Record exceptions for unsupported or custom kernels awaiting vendor guidance.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2025-21956 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
1ADP providers
11Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c, 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c, 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c, 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c, 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c, 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c, 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7c, 4562236b3bc0a28aeb6ee93b2d8a849a4c4e1c7cunaffected
LinuxLinux4.15, 0, 5.4.292, 5.10.236, 5.15.180, 6.1.132, 6.6.84, 6.12.20, 6.13.8, 6.14affected
Weakness

CWE details

No CWE listed

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