CVE-2025-46393: ImageMagick MIFF Processing Vulnerability

CVE-2025-46393 Overview

CVE-2025-46393 affects ImageMagick versions prior to 7.1.1-44. The vulnerability resides in the multispectral Magick Image File Format (MIFF) image processing code. The packet_size value is mishandled when rendering all channels in an arbitrary order, resulting in an incorrect buffer size allocation [CWE-131: Incorrect Calculation of Buffer Size]. Attackers can supply a crafted MIFF image to trigger the flawed calculation over the network, impacting integrity of image processing operations. The issue was addressed in the ImageMagick 7.1.1-44 release on 2025-02-22.

Critical Impact
A crafted multispectral MIFF file processed by a vulnerable ImageMagick build can trigger incorrect buffer size calculations, leading to memory corruption risk in image conversion pipelines.

Affected Products

ImageMagick versions prior to 7.1.1-44
Applications and services that embed ImageMagick for MIFF image conversion
Server-side image processing pipelines exposing ImageMagick via web upload endpoints

Discovery Timeline

2025-02-22 - ImageMagick releases version 7.1.1-44 containing the fix
2025-04-23 - CVE-2025-46393 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-46393

Vulnerability Analysis

The defect lives in coders/miff.c, the MIFF image encoder within ImageMagick. When a multispectral image contains meta channels, ImageMagick renders all channels in an arbitrary order. The pre-patch code path added the meta channel contribution to packet_size after applying other adjustments, producing an incorrect per-pixel size when meta channels were present.

Because packet_size drives allocation sizing for compression buffers used by BZipMaxExtent, LZMAMaxExtent, and ZipMaxExtent, an undersized value leads to insufficient buffer space during encoding. This can corrupt output data or produce malformed intermediate state in downstream processing.

The flaw is classified under [CWE-131] (Incorrect Calculation of Buffer Size). It is reachable through any attacker-supplied MIFF file passed to a vulnerable ImageMagick instance, including web services that accept user-uploaded images.

Root Cause

The root cause is order-of-operations in packet_size computation. When image->number_meta_channels != 0, the patched code overrides packet_size with GetImageChannels(image)*image->depth/8, guaranteeing every channel is accounted for before RLE compression adjustment. The prior implementation appended the meta-channel contribution too late and after conditional CMYK adjustments.

Attack Vector

An attacker submits a crafted multispectral MIFF image to a service that invokes ImageMagick for conversion or thumbnail generation. No authentication is required when the endpoint accepts anonymous uploads. Exploitation triggers during MIFF encoding when packet_size is calculated for the output buffer.

// Source: https://github.com/ImageMagick/ImageMagick/commit/81ac8a0d2eb21739842ed18c48c7646b7eef65b8
// Security patch in coders/miff.c
       packet_size+=image->depth/8;
     if (image->colorspace == CMYKColorspace)
       packet_size+=image->depth/8;
+    if (image->number_meta_channels != 0)
+      packet_size=GetImageChannels(image)*image->depth/8;
     if (image->compression == RLECompression)
       packet_size++;
-    if (image->number_meta_channels != 0)
-      packet_size+=image->number_meta_channels*image->depth/8;
     compress_extent=MagickMax(MagickMax(BZipMaxExtent(packet_size*
       image->columns),LZMAMaxExtent(packet_size*image->columns)),
       ZipMaxExtent(packet_size*image->columns));

The patch replaces the additive meta-channel calculation with an assignment based on GetImageChannels(image), ensuring the buffer accommodates all channels rendered in arbitrary order.

Detection Methods for CVE-2025-46393

Indicators of Compromise

MIFF files containing multispectral channel definitions submitted to public-facing upload endpoints
ImageMagick process crashes or abnormal exits during MIFF encoding operations
Unexpected convert, magick, or identify binary invocations spawned from web application service accounts

Detection Strategies

Inventory hosts running ImageMagick and compare installed versions against 7.1.1-44; flag anything older
Inspect image conversion logs for MIFF inputs with non-zero meta-channel counts originating from untrusted sources
Monitor for repeated malformed image submissions to endpoints that invoke ImageMagick

Monitoring Recommendations

Enable ImageMagick logging via policy.xml and forward events to a central log platform for correlation
Alert on ImageMagick child processes exhibiting unusual memory footprints or non-zero exit codes
Track file uploads with .miff extensions or MIFF magic bytes across web application gateways

How to Mitigate CVE-2025-46393

Immediate Actions Required

Upgrade ImageMagick to 7.1.1-44 or later on all servers, containers, and developer workstations
Rebuild container images that bundle ImageMagick and redeploy affected workloads
Restrict MIFF input handling in policy.xml if an upgrade cannot be applied immediately

Patch Information

The fix is committed upstream in the ImageMagick repository at commit 81ac8a0d2eb21739842ed18c48c7646b7eef65b8 and shipped in release 7.1.1-44 on 2025-02-22. Details are available in the ImageMagick Changelog Entry and the GitHub Commit Notice. Downstream Linux distributions should be tracked for backported packages.

Workarounds

Disable the MIFF coder in policy.xml where MIFF processing is not required
Validate uploaded image MIME types and reject MIFF files at the application layer
Run ImageMagick in a sandboxed process with restricted memory limits and seccomp filters

bash

# /etc/ImageMagick-7/policy.xml - disable MIFF coder as a workaround
<policymap>
  <policy domain="coder" rights="none" pattern="MIFF" />
</policymap>