dbcve.org
Debian LinuxOperating system · Debian

CVE-2021-32493

HIGH · 7.8 CVSS v3.1 Published 2021-06-24
Fix available
A fix is available. Upgrade to after 3.5.28 or later.
See remediation →
81/100
Remediation priority · High
No privileges

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 · unedited
A flaw was found in djvulibre-3.5.28 and earlier. A heap buffer overflow in function DJVU::GBitmap::decode() via crafted djvu file may lead to application crash and other consequences.

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 confidence

A heap buffer overflow vulnerability exists in djvulibre versions 3.5.28 and earlier in the DJVU::GBitmap::decode() function. When processing a specially crafted DJVU file, the decoder fails to properly validate input bounds before writing to heap memory, allowing an attacker to overflow allocated buffers and potentially execute arbitrary code or cause denial of service.

MitigationUpgrade djvulibre to a version newer than 3.5.28. If upgrade is not immediately feasible, implement input validation and file size limits on DJVU files before processing, and consider running the application in a sandboxed environment to limit exploitation impact.

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
Affected:= 10.0= 11.0
DjvulibreApplication
Affected:<= 3.5.28

CVSS 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
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check if djvulibre is installed
    On Debian-based systems, run: dpkg -l | grep -i djvulibre or check for package files in /var/lib/dpkg/info/
    Affected if No package named djvulibre is found, meaning the software is not installed and not affected
  2. Identify installed djvulibre version
    Run: dpkg -l djvulibre (Debian) or rpm -qi djvulibre (RPM-based) to retrieve the installed version number
    Affected if The installed version is 3.5.28 or earlier, or the version cannot be determined (indicating very old or unpatched installation)
  3. Check for libdjvulibre library
    Run: locate libdjvulibre.so or check /usr/lib/ and /usr/lib64/ directories for libdjvulibre files. Also run: ldd <application> | grep djvu to find linked applications
    Affected if The shared library exists and its version matches the vulnerable version range
  4. Identify applications using djvulibre
    Run: apt-cache rdepends djvulibre or check for installed programs like ddjvu, djvutoxml, c44, or any application that processes .djvu files
    Affected if Applications that process DJVU files are installed and linked against the vulnerable library
  5. Verify DJVU file processing capability
    Check if any application on the system is configured to handle .djvu files: file /usr/bin/*djvu* or look for MIME type handlers for image/djvu
    Affected if The system has tools or applications capable of decoding DJVU files using the vulnerable library

A system is affected if djvulibre version 3.5.28 or earlier is installed and there are applications or tools present that can decode DJVU files using the vulnerable DJVU::GBitmap::decode() function.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to a release after 3.5.28
Interim mitigation

Upgrade djvulibre to a version newer than 3.5.28. If upgrade is not immediately feasible, implement input validation and file size limits on DJVU files before processing, and consider running the application in a sandboxed environment to limit exploitation impact.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-32493 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data