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CVE Record

CVE-2021-47108: drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf

In the Linux kernel, the following vulnerability has been resolved: drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf In commit 41ca9caaae0b ("drm/mediatek: hdmi: Add check for CEA modes only") a check for CEA modes was added to function mtk_hdmi_bridge_mode_valid() in order to address possible issues on MT8167; moreover, with commit c91026a938c2 ("drm/mediatek: hdmi: Add optional limit on maximal HDMI mode clock") another similar check was introduced. Unfortunately though, at the time of writing, MT8173 does not provide any mtk_hdmi_conf structure and this is crashing the kernel with NULL pointer upon entering mtk_hdmi_bridge_mode_valid(), which happens as soon as a HDMI cable gets plugged in. To fix this regression, add a NULL pointer check for hdmi->conf in the said function, restoring HDMI functionality and avoiding NULL pointer kernel panics.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This is a Linux kernel crash bug in the MediaTek HDMI driver. On affected systems, plugging in an HDMI cable can trigger a NULL pointer kernel panic, disrupting availability. The public source points to a hardware-specific regression rather than broad remote compromise.

Executive priority

Treat this as a targeted availability risk for affected MediaTek-based Linux devices. It is unlikely to drive broad emergency response, but devices with accessible HDMI ports should be patched in normal maintenance cycles.

Technical view

mtk_hdmi_bridge_mode_valid() dereferenced hdmi->conf after earlier HDMI mode checks were added. MT8173 did not provide mtk_hdmi_conf, so entering that path could panic the kernel. The stable fix adds a NULL check before using the configuration pointer.

Likely exposure

Exposure appears limited to Linux systems using the MediaTek DRM HDMI driver, especially MT8173 platforms, on source-listed affected kernel versions including 5.14, 5.15.12, and 5.16. Downstream vendor backports need verification.

Exploitation context

The source describes a crash when an HDMI cable is plugged in. No KEV listing or provided source states active exploitation. Evidence supports local or physical availability impact, not remote code execution.

Researcher notes

The public record lacks CVSS, CWE, and detailed downstream version ranges. The key differentiator is whether hdmi->conf can be NULL on the deployed platform and whether the stable NULL-check fix is backported.

Mitigation direction

  • Update to a kernel containing the referenced stable fixes.
  • Check device vendor advisories for backported MediaTek HDMI driver patches.
  • Prioritize exposed appliances or kiosks where HDMI access is possible.
  • If updates are unavailable, restrict physical HDMI access where practical.

Validation and detection

  • Inventory Linux devices using MediaTek HDMI hardware or MT8173 platforms.
  • Confirm running kernel version and downstream patch status.
  • Review kernel logs for HDMI-related NULL pointer panics.
  • Verify the fix is present through vendor release notes or stable commit backports.
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-2021-47108 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
LinuxLinux41ca9caaae0bfc959b22dbcd59d88a7107707e17, 41ca9caaae0bfc959b22dbcd59d88a7107707e17unaffected
LinuxLinux5.14, 0, 5.15.12, 5.16affected
Weakness

CWE details

No CWE listed

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