CVE-2026-26983: ImageMagick Use-After-Free Vulnerability

CVE-2026-26983 Overview

A use-after-free vulnerability exists in ImageMagick's MSL (Magick Scripting Language) interpreter that can be triggered when processing an invalid <map> element. The flaw causes the MSL interpreter to crash by referencing an image object after it has been deallocated from memory. This vulnerability affects ImageMagick versions prior to 7.1.2-15 and 6.9.13-40.

Critical Impact

Attackers can cause denial of service conditions by supplying maliciously crafted MSL input containing invalid <map> elements, potentially disrupting image processing services and applications relying on ImageMagick.

Affected Products

• ImageMagick versions prior to 7.1.2-15
• ImageMagick versions prior to 6.9.13-40

Discovery Timeline

• 2026-02-24 - CVE CVE-2026-26983 published to NVD
• 2026-02-24 - Last updated in NVD database

Technical Details for CVE-2026-26983

Vulnerability Analysis

This vulnerability is classified as both a Use-After-Free (CWE-416) and a Null Pointer Dereference (CWE-476) issue within ImageMagick's MSL interpreter component. The MSL interpreter is responsible for parsing and executing Magick Scripting Language scripts, which provide a powerful interface for batch image processing operations.

When the interpreter encounters a malformed <map> element during MSL script parsing, the image object associated with the map operation is prematurely freed. However, subsequent code paths continue to reference this deallocated memory, leading to undefined behavior. In practice, this results in a crash condition that terminates the ImageMagick process.

The vulnerability can be exploited remotely without authentication by providing malicious MSL input to any application or service that processes user-supplied MSL scripts through ImageMagick. While the immediate impact is limited to denial of service (availability impact), use-after-free conditions can sometimes be leveraged for more severe attacks depending on heap state and memory layout.

Root Cause

The root cause lies in improper memory management within the MSL interpreter's <map> element handling code. When an invalid <map> element is encountered, the error handling path frees the associated image structure but fails to nullify the pointer or prevent subsequent access. This results in dangling pointer references that cause the interpreter to access freed memory.

Attack Vector

The vulnerability is exploitable over the network with low attack complexity. An attacker can craft a malicious MSL script containing an invalid <map> element and submit it to any web application, API endpoint, or service that processes MSL scripts using a vulnerable ImageMagick installation. No authentication or user interaction is required for exploitation.

Common attack scenarios include:

• Uploading malicious MSL files to image processing services
• Submitting crafted MSL content to batch processing APIs
• Exploiting applications that convert user-supplied MSL scripts to images

The vulnerability exploits a flaw in how the MSL interpreter handles the <map> element. When a malformed map structure is parsed, the interpreter incorrectly frees the image object during error handling while retaining a reference to it. Subsequent operations that attempt to access the freed image trigger the use-after-free condition, causing memory corruption and a crash. For detailed technical information, see the ImageMagick Security Advisory.

Detection Methods for CVE-2026-26983

Indicators of Compromise

• Unexpected crashes or segmentation faults in ImageMagick processes during MSL script processing
• Process termination events for convert, magick, or other ImageMagick utilities with crash signatures
• Core dump files indicating use-after-free or null pointer dereference in MSL-related functions
• Unusual MSL script submissions containing malformed <map> elements

Detection Strategies

• Monitor ImageMagick process stability and track abnormal termination events
• Implement input validation to detect and reject malformed MSL scripts before processing
• Deploy application-level logging to capture MSL parsing errors and map element processing failures
• Use memory sanitizers (ASan, MSan) in development environments to detect use-after-free conditions

Monitoring Recommendations

• Enable crash reporting for all ImageMagick processes in production environments
• Configure alerting for repeated ImageMagick process failures within short time windows
• Monitor system logs for segfault signals originating from ImageMagick binaries
• Track file uploads and API requests containing MSL content for anomalous patterns

How to Mitigate CVE-2026-26983

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
• Review and restrict MSL script processing capabilities if not required
• Implement input validation to sanitize MSL content before processing

Patch Information

ImageMagick has released patched versions that address this vulnerability. The fix is included in versions 7.1.2-15 and 6.9.13-40. Users should upgrade to these versions or later to remediate the vulnerability. Detailed patch information is available in the ImageMagick Security Advisory.

Workarounds

• Disable MSL script processing entirely if the functionality is not required by your application
• Implement strict input validation to reject MSL scripts containing <map> elements from untrusted sources
• Run ImageMagick processes in sandboxed environments to limit the impact of crashes
• Use ImageMagick's policy.xml configuration to restrict MSL coder access

# Disable MSL coder in ImageMagick policy.xml
# Add the following to /etc/ImageMagick-7/policy.xml or equivalent
<policy domain="coder" rights="none" pattern="MSL" />