ImageMagick affected by divide-by-zero in ThumbnailImage via montage -geometry ":" leads to crash
Date: 2025-08
Affected: nuget/Magick.NET-Q8-x86, nuget/Magick.NET-Q8-x64, nuget/Magick.NET-Q8-arm64
Attack vector: dos
Category: vulnerability-disclosure
Severity: Low
CVE: CVE-2025-55212
CWE: CWE-369
CVSS: 3.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L)

## 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: ``` .


Mitigations:

Architectural layers (MAESTRO):