CVE-2026-56362: ImageMagick Buffer Overflow Vulnerability

CVE-2026-56362 Overview

CVE-2026-56362 is a heap-buffer-overflow read vulnerability in ImageMagick versions prior to 7.1.2-15. The flaw resides in the GetPixelIndex function and stems from OpenPixelCache updating image channel metadata before pixel cache memory allocation completes. When memory or disk allocation fails during cache initialization, the channel metadata remains desynchronized from the actual buffer state. Any writer that subsequently calls GetPixelIndex reads past the allocated heap buffer. The issue is tracked under [CWE-125] Out-of-Bounds Read.

Critical Impact
Attackers who can influence image processing under resource-constrained conditions can trigger out-of-bounds heap reads, potentially disclosing adjacent memory contents through any ImageMagick writer that invokes GetPixelIndex.

Affected Products

ImageMagick versions prior to 7.1.2-15
Applications and services embedding vulnerable ImageMagick libraries
Image processing pipelines relying on MagickCore pixel cache operations

Discovery Timeline

2026-07-08 - CVE-2026-56362 published to the National Vulnerability Database
2026-07-09 - Last updated in NVD database

Technical Details for CVE-2026-56362

Vulnerability Analysis

The vulnerability arises from a state desynchronization between image channel metadata and the underlying pixel cache buffer. OpenPixelCache is responsible for allocating memory or disk-backed storage for pixel data. In the vulnerable code path, the function updates the image's channel metadata fields before completing the allocation step. When the subsequent allocation fails, execution returns to the caller with metadata that describes a buffer larger than what actually exists.

Any writer routine that later invokes GetPixelIndex uses the stale metadata to compute read offsets. This results in a heap-buffer-overflow read, exposing bytes from adjacent heap regions. The condition is deterministic when an attacker can control image dimensions or channel counts and can induce allocation failure through resource pressure. Impact is limited to information disclosure of adjacent heap memory, consistent with the low confidentiality impact indicated in the CVSS 4.0 vector.

Root Cause

The root cause is an ordering defect in OpenPixelCache. Channel metadata mutation occurs before the allocation completes and before the function verifies allocation success. There is no rollback of metadata when allocation fails, leaving the image object in an inconsistent state that violates the invariants assumed by pixel accessor functions like GetPixelIndex.

Attack Vector

Exploitation requires an attacker to submit a crafted image to a target that uses ImageMagick and to induce a memory or disk allocation failure during pixel cache initialization. High attack complexity applies because the attacker must satisfy resource-exhaustion preconditions and hold elevated privileges within the processing context. Successful exploitation causes a downstream writer to perform an out-of-bounds read, which can leak heap contents into rendered output or error paths. See the VulnCheck Advisory on ImageMagick for technical details.

Detection Methods for CVE-2026-56362

Indicators of Compromise

Repeated ImageMagick process crashes or abnormal exits during image conversion operations
Error log entries from MagickCore referencing pixel cache allocation failures followed by successful writer output
Unusually large or malformed input images submitted immediately before allocation-failure log events

Detection Strategies

Inventory installed ImageMagick versions across servers and containers and flag any build prior to 7.1.2-15
Enable AddressSanitizer or Valgrind in staging environments to catch out-of-bounds reads in GetPixelIndex during regression testing
Instrument image-processing services to log allocation failures reported by OpenPixelCache and correlate them with subsequent writer invocations

Monitoring Recommendations

Monitor memory pressure and cgroup OOM events on hosts running ImageMagick workloads, since allocation failures are a precondition for exploitation
Alert on unexpected content patterns in generated image outputs that could indicate leaked heap bytes embedded in pixel data
Track ImageMagick package versions through software composition analysis and vulnerability scanning tools

How to Mitigate CVE-2026-56362

Immediate Actions Required

Upgrade ImageMagick to version 7.1.2-15 or later on all systems, including container images and build pipelines
Rebuild and redeploy any applications that statically link or bundle MagickCore libraries
Restrict image processing to authenticated users where feasible, given the high privileges required for exploitation

Patch Information

The vulnerability is fixed in ImageMagick 7.1.2-15. Details are available in the GitHub Security Advisory GHSA-gq5v-qf8q-fp77. Distribution maintainers should track backports for long-term support branches and apply vendor updates as they become available.

Workarounds

Enforce strict input validation on image dimensions and channel counts to reduce the attack surface for allocation-failure triggers
Apply resource limits and memory quotas that fail image processing early rather than allowing partial cache initialization
Run ImageMagick processing in isolated sandboxes or dedicated containers to contain any information disclosure to non-sensitive memory regions

bash

# Verify installed ImageMagick version and upgrade
magick -version
# Debian/Ubuntu
sudo apt-get update && sudo apt-get install --only-upgrade imagemagick
# RHEL/CentOS/Fedora
sudo dnf upgrade ImageMagick
# Confirm version is 7.1.2-15 or later
magick -version | grep -Eo '7\.[0-9]+\.[0-9]+-[0-9]+'