Debian LinuxOperating system · Debian
CVE-2021-20176
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 · uneditedA divide-by-zero flaw was found in ImageMagick 6.9.11-57 and 7.0.10-57 in gem.c. This flaw allows an attacker who submits a crafted file that is processed by ImageMagick to trigger undefined behavior through a division by zero. The highest threat from this vulnerability is to system availability.
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 · moderate confidenceA divide-by-zero vulnerability exists in ImageMagick versions 6.9.11-57 and 7.0.10-57 in the gem.c file. An attacker can trigger this flaw by submitting a crafted image file for processing by ImageMagick, causing undefined behavior through division by zero that primarily impacts system availability.
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 data
Debian LinuxOperating system
= 9.0< 6.9.11-57>= 7.0.0-0, < 7.0.10-56CVSS 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
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/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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Check installed ImageMagick versionRun `identify -version` or `convert -version` to see the installed versionAffected if Version is 6.9.11-57 or below in the 6.9.x line, or 7.0.10-56 or below in the 7.0.x line (specifically < 6.9.11-57 or >= 7.0.0-0 and < 7.0.10-56)
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Verify the gem.c file is present in the buildLocate the ImageMagick source or binary and check for the presence of gem.c in the coders directory (typically found at /usr/include/ImageMagick or within the installed package)Affected if The vulnerable code path exists in the installed version and the image processing coders are compiled in
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Confirm ImageMagick policy allows processing of untrusted imagesCheck the policy.xml configuration file (usually at /etc/ImageMagick-6/policy.xml or /etc/ImageMagick/policy.xml) for any restrictions on image processing. Run `identify -list policy` to see current policy settingsAffected if Policy does not restrict the image type being processed, allowing untrusted image files to reach the vulnerable code path
You are affected if ImageMagick is installed with a version in the vulnerable range (pre-6.9.11-57 or pre-7.0.10-56) AND the system processes untrusted image files without input validation or policy restrictions in place.
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 data6.9.11-577.0.10-56
Update ImageMagick to a version beyond 6.9.11-57 or 7.0.10-57 that contains the fix, or implement input validation to reject malformed image files before processing by ImageMagick.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20176 — 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-2021-20176 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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