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CVE Record

CVE-2021-47533: drm/vc4: kms: Clear the HVS FIFO commit pointer once done

In the Linux kernel, the following vulnerability has been resolved: drm/vc4: kms: Clear the HVS FIFO commit pointer once done Commit 9ec03d7f1ed3 ("drm/vc4: kms: Wait on previous FIFO users before a commit") introduced a wait on the previous commit done on a given HVS FIFO. However, we never cleared that pointer once done. Since drm_crtc_commit_put can free the drm_crtc_commit structure directly if we were the last user, this means that it can lead to a use-after free if we were to duplicate the state, and that stale pointer would even be copied to the new state. Set the pointer to NULL once we're done with the wait so that we don't carry over a pointer to a free'd structure.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue affects the vc4 display subsystem. A stale internal pointer could be reused after its memory was freed, creating a use-after-free condition. The sources do not provide a CVSS score, exploitation evidence, or business-impact detail, so urgency depends mainly on whether affected kernels and this display path are present.

Executive priority

Set priority after exposure confirmation. If vc4 is not used, business urgency is likely lower. If affected display systems are in production, schedule kernel remediation through normal patch governance and monitor vendor advisories.

Technical view

In drm/vc4 KMS, a previous HVS FIFO commit pointer was waited on but not cleared. Because drm_crtc_commit_put can free the commit object, duplicated state could copy a stale pointer and later dereference freed memory. The fix clears the pointer after the wait completes.

Likely exposure

Exposure appears tied to Linux kernels containing the affected vc4 DRM/KMS code. The bundle lists Linux versions including 5.12, 5.15.7, and 5.16 as affected, but distribution-specific package status is not provided.

Exploitation context

The source bundle does not show CISA KEV listing, public exploitation, exploit code, or attacker prerequisites. Treat this as a kernel memory-safety flaw requiring exposure confirmation, not as known active exploitation.

Researcher notes

The key condition is stale drm_crtc_commit state copied after drm_crtc_commit_put may free the object. The provided record lacks CVSS, CWE, exploitability analysis, and distribution mappings, so conclusions beyond affected code and remediation commits are limited.

Mitigation direction

  • Check Linux vendor or distribution advisories for fixed kernel packages.
  • Update affected systems to a kernel containing the referenced stable fixes.
  • Prioritize systems that actually load or depend on the vc4 DRM/KMS driver.
  • If no vendor fix is available, follow vendor guidance rather than applying ad hoc changes.

Validation and detection

  • Inventory running kernel versions across Linux assets.
  • Check whether the vc4 DRM/KMS driver is present or loaded.
  • Compare deployed kernel source or package changelog against the referenced fixes.
  • Record distribution advisory status because the bundle lacks package-level fixed versions.
Prepared
Confidence
medium
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

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CVE-2021-47533 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
2ADP providers
3Source links

SSVC decision data

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

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
other: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.