GHSA-9VJ4-WC7R-P844

Vulnerability from github – Published: 2026-01-21 01:05 – Updated: 2026-01-21 01:05
VLAI?
Summary
ImageMagick MSL: Stack overflow via infinite recursion in ProcessMSLScript
Details

Summary

Stack overflow via infinite recursion in MSL (Magick Scripting Language) <write> command when writing to MSL format.

Version

  • ImageMagick 7.x (tested on current main branch)
  • Commit: HEAD
  • Requires: libxml2 support (for MSL parsing)

Steps to Reproduce

Method 1: Using ImageMagick directly

magick MSL:recursive.msl out.png

Method 2: Using OSS-Fuzz reproduce

python3 infra/helper.py build_fuzzers imagemagick
python3 infra/helper.py reproduce imagemagick msl_fuzzer recursive.msl

Or run the fuzzer directly:

./msl_fuzzer recursive.msl

Expected Behavior

ImageMagick should handle recursive MSL references gracefully by detecting the loop and returning an error.

Actual Behavior

Stack overflow causes process crash:

AddressSanitizer:DEADLYSIGNAL
==PID==ERROR: AddressSanitizer: stack-overflow
    #0 MSLStartElement /src/imagemagick/coders/msl.c:7045
    #1 xmlParseStartTag /src/libxml2/parser.c
    #2 xmlParseChunk /src/libxml2/parser.c:11273
    #3 ProcessMSLScript /src/imagemagick/coders/msl.c:7405
    #4 WriteMSLImage /src/imagemagick/coders/msl.c:7867
    #5 WriteImage /src/imagemagick/MagickCore/constitute.c:1346
    #6 MSLStartElement /src/imagemagick/coders/msl.c:7045
    ... (infinite recursion, 287+ frames)

Root Cause Analysis

In coders/msl.c, the <write> command handler in MSLStartElement() (line ~7045) calls WriteImage(). When the output filename specifies MSL format (msl:filename), WriteMSLImage() is called, which parses the MSL file again via ProcessMSLScript().

If the MSL file references itself (directly or indirectly), this creates an infinite recursion loop:

MSLStartElement() → WriteImage() → WriteMSLImage() → ProcessMSLScript()
    → xmlParseChunk() → MSLStartElement() → ... (infinite loop)

Impact

  • DoS: Guaranteed crash via stack exhaustion
  • Affected: Any application using ImageMagick to process user-supplied MSL files

Additional Trigger Paths

The <read> command can also trigger recursion:

Indirect recursion is also possible (a.msl → b.msl → a.msl).

Fuzzer

This issue was discovered using a custom MSL fuzzer:

#include <cstdint>
#include <Magick++/Blob.h>
#include <Magick++/Image.h>
#include "utils.cc"

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
{
  if (IsInvalidSize(Size))
    return(0);
  try
  {
    const Magick::Blob blob(Data, Size);
    Magick::Image image;
    image.magick("MSL");
    image.fileName("MSL:");
    image.read(blob);
  }
  catch (Magick::Exception)
  {
  }
  return(0);
}

This issue was found by Team FuzzingBrain @ Texas A&M University

Show details on source website

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  ],
  "aliases": [
    "CVE-2026-23874"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-21T01:05:23Z",
    "nvd_published_at": "2026-01-20T01:15:57Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nStack overflow via infinite recursion in MSL (Magick Scripting Language) `\u003cwrite\u003e` command when writing to MSL format.\n\n## Version\n\n- ImageMagick 7.x (tested on current main branch)\n- Commit: HEAD\n- Requires: libxml2 support (for MSL parsing)\n\n## Steps to Reproduce\n\n### Method 1: Using ImageMagick directly\n\n```bash\nmagick MSL:recursive.msl out.png\n```\n\n### Method 2: Using OSS-Fuzz reproduce\n\n```bash\npython3 infra/helper.py build_fuzzers imagemagick\npython3 infra/helper.py reproduce imagemagick msl_fuzzer recursive.msl\n```\n\nOr run the fuzzer directly:\n```bash\n./msl_fuzzer recursive.msl\n```\n\n## Expected Behavior\n\nImageMagick should handle recursive MSL references gracefully by detecting the loop and returning an error.\n\n## Actual Behavior\n\nStack overflow causes process crash:\n\n```\nAddressSanitizer:DEADLYSIGNAL\n==PID==ERROR: AddressSanitizer: stack-overflow\n    #0 MSLStartElement /src/imagemagick/coders/msl.c:7045\n    #1 xmlParseStartTag /src/libxml2/parser.c\n    #2 xmlParseChunk /src/libxml2/parser.c:11273\n    #3 ProcessMSLScript /src/imagemagick/coders/msl.c:7405\n    #4 WriteMSLImage /src/imagemagick/coders/msl.c:7867\n    #5 WriteImage /src/imagemagick/MagickCore/constitute.c:1346\n    #6 MSLStartElement /src/imagemagick/coders/msl.c:7045\n    ... (infinite recursion, 287+ frames)\n```\n\n## Root Cause Analysis\n\nIn `coders/msl.c`, the `\u003cwrite\u003e` command handler in `MSLStartElement()` (line ~7045) calls `WriteImage()`. When the output filename specifies MSL format (`msl:filename`), `WriteMSLImage()` is called, which parses the MSL file again via `ProcessMSLScript()`.\n\nIf the MSL file references itself (directly or indirectly), this creates an infinite recursion loop:\n\n```\nMSLStartElement() \u2192 WriteImage() \u2192 WriteMSLImage() \u2192 ProcessMSLScript()\n    \u2192 xmlParseChunk() \u2192 MSLStartElement() \u2192 ... (infinite loop)\n```\n\n## Impact\n\n- **DoS**: Guaranteed crash via stack exhaustion\n- **Affected**: Any application using ImageMagick to process user-supplied MSL files\n\n## Additional Trigger Paths\n\nThe `\u003cread\u003e` command can also trigger recursion:\n\nIndirect recursion is also possible (a.msl \u2192 b.msl \u2192 a.msl).\n\n## Fuzzer\n\nThis issue was discovered using a custom MSL fuzzer:\n\n```cpp\n#include \u003ccstdint\u003e\n#include \u003cMagick++/Blob.h\u003e\n#include \u003cMagick++/Image.h\u003e\n#include \"utils.cc\"\n\nextern \"C\" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)\n{\n  if (IsInvalidSize(Size))\n    return(0);\n  try\n  {\n    const Magick::Blob blob(Data, Size);\n    Magick::Image image;\n    image.magick(\"MSL\");\n    image.fileName(\"MSL:\");\n    image.read(blob);\n  }\n  catch (Magick::Exception)\n  {\n  }\n  return(0);\n}\n```\n\nThis issue was found by Team FuzzingBrain @ Texas A\u0026M University",
  "id": "GHSA-9vj4-wc7r-p844",
  "modified": "2026-01-21T01:05:23Z",
  "published": "2026-01-21T01:05:23Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ImageMagick/ImageMagick/security/advisories/GHSA-9vj4-wc7r-p844"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23874"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ImageMagick/ImageMagick"
    },
    {
      "type": "WEB",
      "url": "https://github.com/dlemstra/Magick.NET/releases/tag/14.10.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ImageMagick MSL: Stack overflow via infinite recursion in ProcessMSLScript"
}


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