CVE-2026-25988: ImageMagick Use-After-Free Vulnerability

CVE-2026-25988 Overview

A memory leak vulnerability has been identified in ImageMagick, the widely-used open-source image processing software suite. The vulnerability exists in msl.c where the stack index fails to update properly under certain conditions, causing images to be stored in incorrect slots and never freed when errors occur. This leads to memory leaks that can be exploited to cause denial of service through resource exhaustion.

Critical Impact

Attackers can exploit this memory leak vulnerability remotely without authentication to cause denial of service conditions by exhausting available memory resources on systems running vulnerable ImageMagick versions.

Affected Products

• ImageMagick versions prior to 7.1.2-15
• ImageMagick versions prior to 6.9.13-40
• Applications and services that process images using vulnerable ImageMagick libraries

Discovery Timeline

• 2026-02-24 - CVE-2026-25988 published to NVD
• 2026-02-25 - Last updated in NVD database

Technical Details for CVE-2026-25988

Vulnerability Analysis

This vulnerability is classified as CWE-401 (Missing Release of Memory after Effective Lifetime), a memory leak condition that occurs within ImageMagick's MSL (Magick Scripting Language) processing component. The flaw stems from improper stack index management during image processing operations.

When processing certain image operations, the msl.c component fails to properly update its internal stack index tracking mechanism. This causes images to be stored in incorrect memory slots during error conditions. Since the images are stored in the wrong slot, the error handling code cannot properly locate and free them, resulting in orphaned memory allocations that persist until the process terminates.

The vulnerability is network-accessible, meaning attackers can trigger it by submitting specially crafted image files or MSL scripts to applications that use ImageMagick for image processing. This is particularly concerning for web applications that allow user-uploaded images to be processed by ImageMagick.

Root Cause

The root cause lies in the improper synchronization between the stack index state and the actual storage location of image objects within msl.c. During error handling paths, the code assumes the current stack index points to the allocated image, but due to the missing update, the image resides in a different slot. The cleanup routine then operates on the wrong memory location, leaving the actual image allocation unreleased.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Crafting malicious image files or MSL scripts designed to trigger error conditions in the vulnerable code path
2. Submitting these files to any service that processes images using vulnerable ImageMagick versions
3. Repeatedly triggering the vulnerability to gradually exhaust server memory
4. Causing denial of service when memory resources are depleted

The vulnerability mechanism involves the MSL parser's stack management during image processing operations. When errors occur in specific processing paths, the stack index is not properly decremented or updated, causing a mismatch between expected and actual image storage locations. Technical details can be found in the GitHub Security Advisory.

Detection Methods for CVE-2026-25988

Indicators of Compromise

• Abnormal memory growth in processes using ImageMagick libraries
• Gradual memory exhaustion on servers processing user-uploaded images
• Process crashes or OOM (Out of Memory) killer events related to ImageMagick processes
• Increased swap usage correlating with image processing activity

Detection Strategies

• Monitor ImageMagick process memory usage for unusual growth patterns over time
• Implement memory consumption thresholds and alerts for image processing services
• Log and analyze image processing errors, particularly those involving MSL operations
• Deploy application-level monitoring to track memory allocation patterns

Monitoring Recommendations

• Configure system monitoring to alert on processes exceeding expected memory thresholds
• Implement process-level resource limits (cgroups, ulimit) to contain memory leak impact
• Monitor for repeated image processing failures that might indicate exploitation attempts
• Track memory utilization trends on systems running ImageMagick-dependent applications

How to Mitigate CVE-2026-25988

Immediate Actions Required

• Upgrade ImageMagick to version 7.1.2-15 or later for the 7.x branch
• Upgrade ImageMagick to version 6.9.13-40 or later for the 6.x branch
• Implement memory limits for ImageMagick processes as a temporary measure
• Review and restrict image processing capabilities to only required formats

Patch Information

The ImageMagick project has released patched versions that correct the stack index management issue in msl.c. The fix ensures proper synchronization between stack index updates and image storage operations, preventing orphaned allocations during error conditions.

Patched Versions:

• ImageMagick 7.1.2-15 and later (7.x branch)
• ImageMagick 6.9.13-40 and later (6.x branch)

For detailed information about the vulnerability and the patch, refer to the GitHub Security Advisory GHSA-782x-jh29-9mf7.

Workarounds

• Implement process-level memory limits using cgroups or container resource constraints
• Configure ImageMagick policy.xml to disable MSL processing if not required
• Deploy process watchdogs to restart ImageMagick-dependent services if memory thresholds are exceeded
• Consider using isolated containers for image processing to limit blast radius of memory exhaustion

# Configuration example - Limit ImageMagick resource usage via policy.xml
# Edit /etc/ImageMagick-7/policy.xml or /etc/ImageMagick-6/policy.xml

# Add memory limits to prevent DoS from memory leaks
<policy domain="resource" name="memory" value="256MiB"/>
<policy domain="resource" name="map" value="512MiB"/>
<policy domain="resource" name="disk" value="1GiB"/>

# Disable MSL if not required by your application
<policy domain="coder" rights="none" pattern="MSL"/>