CVE-2021-39814
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn ppmp_validate_wsm of drm_fw.c, there is a possible out of bounds write due to an incorrect bounds check. This could lead to local escalation of privilege with System execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android kernelAndroid ID: A-216792660References: N/A
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA bounds check error in the ppmp_validate_wsm function within the Android kernel's DRM firmware code (drm_fw.c) allows an out-of-bounds write. Since the function validates workspace manager (WSM) structures, incorrect boundary validation permits writing beyond allocated buffers. This enables local privilege escalation from System-level privileges.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE dataall versionsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify the Android kernel versionRun 'uname -r' or check /proc/version to obtain the running kernel versionAffected if The kernel version is unpatched and falls within or before the vulnerable period (2021)
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Check for the presence of drm_fw.c moduleExamine /sys/module/ or /proc/modules for DRM firmware-related modules, or check /proc/kallsyms for symbols related to 'ppmp_validate_wsm'Affected if The kernel contains the vulnerable ppmp_validate_wsm function symbol and the DRM firmware module is loaded
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Verify the DRM subsystem is activeCheck /sys/class/drm/ for DRM devices or run 'lsmod' to see if drm-related kernel modules are loadedAffected if The DRM subsystem with firmware processing is enabled and running
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Confirm system-level privileges are in useIdentify processes running with System-level privileges using 'ps -AZ' or checking uid 1000 (system) processesAffected if The device runs processes at System privilege level, which the vulnerability can escalate to root
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Check vendor kernel source for the vulnerabilityReview the vendor's kernel source code for drm_fw.c, specifically examining the ppmp_validate_wsm function for the bounds check fixAffected if The source code still contains the original vulnerable bounds check logic without the vendor patch
The environment is affected if the Android kernel is from 2021 or earlier, contains the ppmp_validate_wsm function in the DRM firmware code, and the DRM subsystem with WSM validation is enabled.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply the vendor-provided kernel patch that corrects the bounds checking logic in ppmp_validate_wsm. Given this is a kernel DRM driver vulnerability, ensure the fix is integrated into the Android kernel build and deployed via firmware or system update.
- Consultation3.0 h
- Implementation6.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-39814 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-39814 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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