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CVE Record

CVE-2021-47534: drm/vc4: kms: Add missing drm_crtc_commit_put

In the Linux kernel, the following vulnerability has been resolved: drm/vc4: kms: Add missing drm_crtc_commit_put Commit 9ec03d7f1ed3 ("drm/vc4: kms: Wait on previous FIFO users before a commit") introduced a global state for the HVS, with each FIFO storing the current CRTC commit so that we can properly synchronize commits. However, the refcounting was off and we thus ended up leaking the drm_crtc_commit structure every commit. Add a drm_crtc_commit_put to prevent the leakage.

MediumCVSS 4.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue is a memory leak in the vc4 display subsystem. Repeated display commits can leak kernel memory and may eventually affect availability. The public data rates it medium severity and does not show active exploitation.

Executive priority

Treat this as a targeted availability risk, not a broad remote compromise issue. Patch during normal kernel maintenance, faster where vc4 display functionality is important or uptime is sensitive.

Technical view

The vc4 KMS code stored CRTC commit references for FIFO synchronization but missed a drm_crtc_commit_put. That refcounting error leaked drm_crtc_commit objects on every commit. The fix adds the missing put to release the reference.

Likely exposure

Exposure is most likely on Linux systems running affected 5.12 through 5.15.7 or pre-5.16 kernels where the vc4 DRM/KMS path is used. Systems not using that driver path are less likely to be exposed.

Exploitation context

The CVSS vector is local, high complexity, high privileges required, no user interaction, and availability-only impact. The source bundle says KEV is false and provides no cited evidence of active exploitation.

Researcher notes

Evidence is limited to the CVE record and kernel stable fixes. No CWE is listed. Do not assume broader driver impact, exploit availability, or specific downstream package status without vendor confirmation.

Mitigation direction

  • Update to a kernel or distribution package containing the referenced stable fixes.
  • Check Linux distribution advisories for backported fixes and exact package versions.
  • Prioritize systems using the vc4 DRM/KMS driver path.
  • Limit unnecessary high-privilege local access until affected systems are patched.
  • Monitor affected systems for abnormal kernel memory growth or availability symptoms.

Validation and detection

  • Inventory Linux kernel versions against the affected version data.
  • Confirm whether vc4 DRM/KMS is enabled or used on each system.
  • Verify patched kernels include the referenced stable commits or equivalent backport.
  • Review vendor advisories for distribution-specific fixed package names.
  • Check monitoring for memory growth during repeated display commit activity.
Prepared
Confidence
high
Sources
4

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2021-47534 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
4.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H

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.

1CVSS vectors
3Timeline events
2ADP providers
3Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
4.1CVSS 3.1MediumCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H0.53.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

4.1Medium
CVSS 3.1 vector shape for CVE-2021-47534Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux9ec03d7f1ed394897891319a4dda75f52c5d292d, 9ec03d7f1ed394897891319a4dda75f52c5d292dunaffected
LinuxLinux5.12, 0, 5.15.7, 5.16affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.