GHSA-5VX3-WX4Q-6CJ8

Vulnerability from github – Published: 2026-01-21 01:06 – Updated: 2026-01-21 01:06
VLAI
Summary
ImageMagick has a NULL pointer dereference in MSL parser via <comment> tag before image load
Details

Summary

NULL pointer dereference in MSL (Magick Scripting Language) parser when processing <comment> tag before any image is loaded.

Version

  • ImageMagick 7.x (tested on current main branch)
  • Commit: HEAD

Steps to Reproduce

Method 1: Using ImageMagick directly

magick MSL:poc.msl out.png

Method 2: Using OSS-Fuzz reproduce

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

Or run the fuzzer directly:

./msl_fuzzer poc.msl

Expected Behavior

ImageMagick should handle the malformed MSL gracefully and return an error message.

Actual Behavior

convert: MagickCore/property.c:297: MagickBooleanType DeleteImageProperty(Image *, const char *): Assertion `image != (Image *) NULL' failed.
Aborted

Root Cause Analysis

In coders/msl.c:7091, MSLEndElement() calls DeleteImageProperty() on msl_info->image[n] when handling the </comment> end tag without checking if the image is NULL:

if (LocaleCompare((const char *) tag,"comment") == 0 )
  {
    (void) DeleteImageProperty(msl_info->image[n],"comment");  // No NULL check
    ...
  }

When <comment> appears before any <read> operation, msl_info->image[n] is NULL, causing the assertion failure in DeleteImageProperty() at property.c:297.

Impact

  • DoS: Crash via assertion failure (debug builds) or NULL pointer dereference (release builds)
  • Affected: Any application using ImageMagick to process user-supplied MSL files

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

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Show details on source website
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  "aliases": [
    "CVE-2026-23952"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-476"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-21T01:06:51Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nNULL pointer dereference in MSL (Magick Scripting Language) parser when processing `\u003ccomment\u003e` tag before any image is loaded.\n\n## Version\n\n- ImageMagick 7.x (tested on current main branch)\n- Commit: HEAD\n\n## Steps to Reproduce\n\n### Method 1: Using ImageMagick directly\n\n```bash\nmagick MSL:poc.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 poc.msl\n```\n\nOr run the fuzzer directly:\n```bash\n./msl_fuzzer poc.msl\n```\n\n## Expected Behavior\n\nImageMagick should handle the malformed MSL gracefully and return an error message.\n\n## Actual Behavior\n\n```\nconvert: MagickCore/property.c:297: MagickBooleanType DeleteImageProperty(Image *, const char *): Assertion `image != (Image *) NULL\u0027 failed.\nAborted\n```\n\n## Root Cause Analysis\n\nIn `coders/msl.c:7091`, `MSLEndElement()` calls `DeleteImageProperty()` on `msl_info-\u003eimage[n]` when handling the `\u003c/comment\u003e` end tag without checking if the image is NULL:\n\n```c\nif (LocaleCompare((const char *) tag,\"comment\") == 0 )\n  {\n    (void) DeleteImageProperty(msl_info-\u003eimage[n],\"comment\");  // No NULL check\n    ...\n  }\n```\n\nWhen `\u003ccomment\u003e` appears before any `\u003cread\u003e` operation, `msl_info-\u003eimage[n]` is NULL, causing the assertion failure in `DeleteImageProperty()` at `property.c:297`.\n\n## Impact\n\n- **DoS**: Crash via assertion failure (debug builds) or NULL pointer dereference (release builds)\n- **Affected**: Any application using ImageMagick to process user-supplied MSL files\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-5vx3-wx4q-6cj8",
  "modified": "2026-01-21T01:06:51Z",
  "published": "2026-01-21T01:06:51Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ImageMagick/ImageMagick/security/advisories/GHSA-5vx3-wx4q-6cj8"
    },
    {
      "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:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "ImageMagick has a NULL pointer dereference in MSL parser via \u003ccomment\u003e tag before image load"
}



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