dbcve.org
LibsixelApplication · Saitoha

CVE-2019-19636

CRITICAL · 9.8 CVSS v3.1 Published 2019-12-08
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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
An issue was discovered in libsixel 1.8.2. There is an integer overflow in the function sixel_encode_body at tosixel.c.

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 confidence

An integer overflow vulnerability exists in the sixel_encode_body function in tosixel.c in libsixel 1.8.2. The overflow occurs during image data processing when arithmetic operations wrap around due to insufficient integer bounds checking, potentially leading to heap corruption, out-of-bounds memory access, or arbitrary code execution.

MitigationUpgrade to libsixel version 1.8.3 or later which contains the fix for this integer overflow. If upgrade is not immediately feasible, implement input validation to ensure image dimensions and buffer sizes do not exceed INT_MAX before arithmetic operations.

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
LibsixelApplication
Affected:= 1.8.2

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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

  1. Check installed libsixel version
    Run 'libsixel-config --version' or check the library file version with 'strings' on the libsixel library file (e.g., /usr/lib/libsixel.so.1) and look for version strings
    Affected if The version displayed is exactly 1.8.2
  2. Identify libsixel library location
    Use 'ldconfig -p | grep sixel' or 'find /usr -name "*sixel*" 2>/dev/null' to locate the libsixel shared library files
    Affected if libsixel library files exist on the system and version cannot be determined or shows 1.8.2
  3. Check if sixel conversion is in use
    Review application logs or traces for calls to 'sixel_encode_body' function, or check if applications using libsixel (like img2sixel, libsixel-based terminals) are processing untrusted images
    Affected if Applications using libsixel are actively processing image data through the sixel_encode_body function
  4. Verify image processing paths
    If you have access to process memory or can instrument the application, monitor for sixel encoding operations with large image dimensions that could trigger the integer overflow during buffer allocation calculations
    Affected if Large images (width x height x color_depth calculations) are being processed by libsixel 1.8.2

A system is affected if libsixel version 1.8.2 is installed and actively used to process image data through the sixel_encode_body function, as the integer overflow occurs during image dimension calculations.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to libsixel version 1.8.3 or later which contains the fix for this integer overflow. If upgrade is not immediately feasible, implement input validation to ensure image dimensions and buffer sizes do not exceed INT_MAX before arithmetic operations.

Recommended fix Moderate confidence

Upgrade to libsixel version 1.8.3 or later stable release (check GitHub releases for latest version)

  1. 1. Identify the current libsixel version in your environment using: pkg-config --modversion libsixel or sixel-config --version
  2. 2. Download the latest stable release of libsixel from the official GitHub repository: https://github.com/saitoha/libsixel
  3. 3. Verify the release notes or changelog to confirm the integer overflow vulnerability (CVE-2019-19636) is addressed in the target version
  4. 4. Follow the standard build process: ./configure, make, make install (or use your system's package manager if available)
  5. 5. Replace the existing libsixel libraries and binaries with the new version
  6. 6. Restart any services or applications using libsixel to load the updated libraries
  7. 7. Verify the new version is installed correctly: sixel-config --version
Caveat Review release notes for any API changes or backward compatibility concerns between 1.8.2 and the target version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Libsixel Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2019-19636 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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