CVE-2026-56372: ImageMagick Buffer Overflow Vulnerability

CVE-2026-56372 Overview

CVE-2026-56372 is a heap buffer overflow read vulnerability in ImageMagick versions prior to 7.1.2-19. The flaw resides in the magnify operation, where an unrecognized magnify:method value triggers an out-of-bounds read on heap-allocated memory [CWE-122]. Attackers can leverage the condition to read sensitive process memory or cause the ImageMagick process to crash, resulting in denial of service. Exploitation requires local access and user interaction, such as processing a crafted image or command directive. The issue is tracked by the upstream project in a GitHub Security Advisory and by third parties in the Vulncheck Advisory for ImageMagick.

Critical Impact
Unrecognized magnify:method values cause an out-of-bounds heap read that can leak process memory or crash ImageMagick during image processing.

Affected Products

ImageMagick versions before 7.1.2-19
Applications and pipelines that embed ImageMagick libraries such as MagickCore and MagickWand
Downstream distributions packaging vulnerable ImageMagick builds

Discovery Timeline

2026-07-11 - CVE-2026-56372 published to NVD
2026-07-13 - Last updated in NVD database

Technical Details for CVE-2026-56372

Vulnerability Analysis

The vulnerability is a heap-based out-of-bounds read in ImageMagick's magnify operation. ImageMagick exposes several supported values for the magnify:method artifact, each mapped to a specific upscaling algorithm. When the input value does not match any recognized method, the code path fails to constrain subsequent buffer indexing. The result is a read past the end of a heap-allocated buffer that holds intermediate pixel data.

Because the flaw is a read rather than a write, the direct consequence is information disclosure and process instability rather than arbitrary code execution. Disclosed bytes can include adjacent heap metadata, image data from other operations, or pointers useful for bypassing address space layout randomization. In long-running services that reuse ImageMagick workers, repeated triggers may leak sensitive content processed by earlier requests.

Root Cause

The root cause is missing input validation on the magnify:method artifact. The dispatcher accepts the attacker-controlled string and proceeds into magnify logic without confirming that the requested method maps to a defined handler. Without a default branch that rejects unknown values, control flow reaches indexing operations that assume a valid, bounded method identifier.

Attack Vector

The attack vector is local and requires user interaction. An attacker supplies a crafted image, command line, or MagickWand call that sets -define magnify:method=<unrecognized> or an equivalent artifact. A user or automated service then invokes the magnify operation on that input. Web services and batch converters that expose ImageMagick to untrusted images or parameters expand the practical reach of the flaw beyond interactive command-line use.

No verified proof-of-concept code has been published. See the
[Vulncheck Advisory for ImageMagick](https://www.vulncheck.com/advisories/imagemagick-heap-buffer-overflow-read-via-unrecognized-magnify-method)
for upstream technical details.

Detection Methods for CVE-2026-56372

Indicators of Compromise

ImageMagick worker processes terminating with segmentation faults during magnify operations
Log entries showing -define magnify:method= with non-standard or unexpected values
Crash dumps referencing MagnifyImage or related magnify code paths in MagickCore

Detection Strategies

Inventory installed ImageMagick binaries and libraries and flag any version earlier than 7.1.2-19.
Inspect application logs and command histories for magnify:method artifacts containing values outside the documented set.
Correlate abnormal ImageMagick process exits with recent image uploads or conversion jobs to identify targeted triggers.

Monitoring Recommendations

Enable core dump collection for image processing services and review dumps referencing magnify functions.
Monitor CPU, memory, and crash rates of ImageMagick worker pools for anomalies tied to specific inputs.
Alert on repeated failures from the same client IP or user submitting images that reach the magnify code path.

How to Mitigate CVE-2026-56372

Immediate Actions Required

Upgrade ImageMagick to version 7.1.2-19 or later on all systems that process untrusted images.
Restrict who can supply -define artifacts and command-line parameters to ImageMagick in shared services.
Sandbox ImageMagick workers so that memory disclosure cannot cross tenant or trust boundaries.

Patch Information

Upstream fixed the issue in ImageMagick 7.1.2-19. Details and patch references are available in the GitHub Security Advisory GHSA-8vfj-q2cp-5m5j. Distribution maintainers should backport the fix into supported ImageMagick packages and rebuild dependent applications.

Workarounds

Reject or strip the magnify:method artifact from user-controlled inputs at the application layer.
Disallow the magnify operation in ImageMagick's policy.xml where the feature is not required.
Validate that any allowed magnify:method value matches an explicit allow-list before invoking ImageMagick.

bash

# Example: disable the magnify coder in ImageMagick policy.xml
# /etc/ImageMagick-7/policy.xml
<policymap>
  <policy domain="coder" rights="none" pattern="MAGNIFY" />
</policymap>