CVE-2026-34238: ImageMagick Buffer Overflow Vulnerability

CVE-2026-34238 Overview

CVE-2026-34238 is an integer overflow vulnerability in ImageMagick, a widely-used open-source image processing software suite. The vulnerability exists in the despeckle operation and affects 32-bit builds, where an integer overflow condition triggers a heap buffer overflow resulting in an out-of-bounds write. This flaw can be exploited by processing a specially crafted image file, potentially leading to application crashes or denial of service conditions.

Critical Impact

Integer overflow in the despeckle operation causes heap buffer overflow on 32-bit ImageMagick builds, enabling out-of-bounds memory writes that may crash the application or corrupt memory.

Affected Products

• ImageMagick versions prior to 7.1.2-19
• ImageMagick versions prior to 6.9.13-44
• Magick.NET versions prior to 14.12.0

Discovery Timeline

• 2026-04-13 - CVE-2026-34238 published to NVD
• 2026-04-13 - Last updated in NVD database

Technical Details for CVE-2026-34238

Vulnerability Analysis

The vulnerability is classified as CWE-190 (Integer Overflow or Wraparound). When ImageMagick processes certain images using the despeckle operation on 32-bit architecture builds, an arithmetic operation produces a result that exceeds the maximum value representable by the integer data type. This integer overflow condition subsequently causes incorrect memory allocation size calculations, leading to a heap buffer overflow.

The despeckle operation is designed to reduce noise in images by analyzing pixel neighborhoods. During this process, memory buffers are allocated based on computed dimensions. When an integer overflow occurs during size calculations, the allocated buffer becomes smaller than expected, while subsequent write operations assume the correct (larger) size. This mismatch results in an out-of-bounds write condition that corrupts adjacent heap memory.

The vulnerability requires local access to exploit and carries a high complexity requirement. It does not require user authentication but achieves no direct impact on confidentiality or integrity—the primary concern is availability due to the potential for application crashes or denial of service.

Root Cause

The root cause is improper handling of arithmetic operations in the despeckle function on 32-bit builds. When processing images with specific dimensions or characteristics, the multiplication of image dimensions or related values overflows the 32-bit integer boundaries, wrapping around to a smaller value. This results in undersized memory allocation that is later overwritten during image processing operations.

Attack Vector

This vulnerability requires local access to exploit (Attack Vector: Local). An attacker would need to supply a maliciously crafted image file to a vulnerable ImageMagick instance running on a 32-bit system. The attack complexity is high, as successful exploitation depends on specific conditions including the target system architecture and the ability to trigger the despeckle operation with attacker-controlled input.

Attack scenarios include:

• Web applications that process user-uploaded images using ImageMagick on 32-bit servers
• Desktop applications using ImageMagick libraries for image manipulation
• Automated image processing pipelines handling untrusted image files
• Systems using Magick.NET bindings with vulnerable underlying ImageMagick versions

The vulnerability triggers during despeckle operations, so exploitation requires either direct invocation of this operation or processing workflows that automatically apply despeckling filters.

Detection Methods for CVE-2026-34238

Indicators of Compromise

• Unexpected crashes or segmentation faults in ImageMagick processes during image processing
• Memory corruption errors or heap corruption warnings in system logs
• ImageMagick processes consuming excessive memory before crashing
• Core dumps indicating buffer overflow conditions in despeckle-related functions

Detection Strategies

• Monitor ImageMagick process stability and track crash frequency, particularly during despeckle operations
• Implement file integrity monitoring for ImageMagick binaries to detect tampering
• Review application logs for repeated image processing failures with specific image files
• Deploy runtime application self-protection (RASP) to detect heap overflow attempts

Monitoring Recommendations

• Enable verbose logging for image processing applications to capture operation details before crashes
• Implement health checks for image processing services to detect availability issues
• Monitor system memory usage patterns for anomalies during image processing workloads
• Configure crash reporting systems to collect and analyze ImageMagick core dumps

How to Mitigate CVE-2026-34238

Immediate Actions Required

• Upgrade ImageMagick to version 7.1.2-19 or later for the 7.x branch
• Upgrade ImageMagick to version 6.9.13-44 or later for the 6.x branch
• Update Magick.NET to version 14.12.0 or later if using .NET bindings
• Prioritize patching 32-bit deployments as 64-bit builds are not affected by this specific overflow

Patch Information

The ImageMagick project has released security patches addressing this vulnerability. The fix is available in ImageMagick version 7.1.2-19 and version 6.9.13-44. The specific code changes can be reviewed in the GitHub commit bcd8519c70ecd9ebbc180920f2cf97b267d1f440. For users of the .NET bindings, Magick.NET version 14.12.0 includes the patched ImageMagick libraries. Additional details are available in the GitHub Security Advisory GHSA-26qp-ffjh-2x4v.

Workarounds

• Migrate 32-bit ImageMagick deployments to 64-bit systems where the integer overflow does not occur
• Disable or restrict access to the despeckle operation in ImageMagick policies if not required
• Implement input validation to reject images with suspicious dimensions before processing
• Use ImageMagick policy files to limit resource consumption and reduce exploitation impact

# ImageMagick policy configuration to restrict despeckle operation
# Add to /etc/ImageMagick-7/policy.xml or equivalent location
# Restrict resource usage to limit impact of potential exploitation
<policy domain="resource" name="memory" value="256MiB"/>
<policy domain="resource" name="map" value="512MiB"/>
<policy domain="resource" name="width" value="16KP"/>
<policy domain="resource" name="height" value="16KP"/>
<policy domain="resource" name="area" value="128MP"/>