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GHSA-fh55-q5pj-pxgw

LowCVSS 3.7 / 10
Published Aug 26, 2025·Last modified Nov 3, 2025
Affected Components(0)

No affected components available

Description

Summary

Passing a geometry string containing only a colon (":") to montage -geometry leads GetGeometry() to set width/height to 0. Later, ThumbnailImage() divides by these zero dimensions, triggering a crash (SIGFPE/abort), resulting in a denial of service.

Details

Root Cause

  1. montage -geometry ":" ... reaches MagickCore/geometry.c:GetGeometry().
  2. StringToDouble/InterpretLocaleValue parses ":" as 0.0; then: https://github.com/ImageMagick/ImageMagick/blob/0ba1b587be17543b664f7ad538e9e51e0da59d17/MagickCore/geometry.c#L355 WidthValue (and/or HeightValue) is set with a zero dimension.
  3. In MagickCore/resize.c:ThumbnailImage(), the code computes: https://github.com/ImageMagick/ImageMagick/blob/0ba1b587be17543b664f7ad538e9e51e0da59d17/MagickCore/resize.c#L4625-L4629 causing a division by zero and immediate crash.

The issue is trivially triggerable without external input files (e.g., using xc:white).

Reproduction

Environment

Version: ImageMagick 7.1.2-1 (Beta) Q16-HDRI x86_64 0ba1b587b:20250812 https://imagemagick.org
Features: Cipher DPC HDRI
Delegates (built-in): bzlib fontconfig freetype jbig jng jpeg lcms lzma pangocairo png tiff x xml zlib
Compiler: clang (14.0.0)
OS/Arch: Linux x86_64

Steps

./bin/magick montage -geometry : xc:white null:

Observed result

IOT instruction (core dumped)
# (Environment-dependent: SIGFPE/abort may be observed.)

PoC

No external file required; the pseudo image xc:white suffices:

./bin/magick montage -geometry : xc:white null:

Impact

  • Denial of Service: A divide-by-zero in ThumbnailImage() causes immediate abnormal termination (e.g., SIGFPE/abort), crashing the ImageMagick process.

Suggested fix

Defensively reject zero dimensions early in ThumbnailImage():

if ((columns == 0) || (rows == 0)) {
  (void) ThrowMagickException(exception, GetMagickModule(), OptionError,
    "InvalidGeometry", "thumbnail requires non-zero dimensions: %.20gx%.20g",
    (double) columns, (double) rows);
  return (Image *) NULL;
}

Additionally, consider tightening validation in GetGeometry() so that colon-only (and similar malformed) inputs do not yield WidthValue/HeightValue with zero, or are rejected outright. Variants like "x:" or ":x" may also need explicit handling (maintainer confirmation requested).

Credits

Team Daemon Fuzz Hunters

Bug Hunting Master Program, HSpace/Findthegap <br>

Woojin Park @jin-156 1203kids@gmail.com

Hojun Lee @leehohojune leehojune@korea.ac.kr

Youngin Won @amethyst0225 youngin04@korea.ac.kr

Siyeon Han @hanbunny kokosyeon@gmail.com

Risk Scores
Base Score
3.7

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the availability of the system.

Threat Intelligence
3.4

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.85%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Low severity
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