CVE-2026-28493: 
C# vulnerability analysis and mitigation

CVE-2026-28493 is an integer overflow vulnerability in the SIXEL decoder of ImageMagick that allows a remote attacker to perform an out-of-bounds write via a specially crafted image file. It affects all ImageMagick versions prior to 7.1.2-16, as well as Magick.NET NuGet packages prior to version 14.10.4. The vulnerability was published on March 9, 2026, by GitHub (assigned by GitHub_M) and carries a CVSS v3.1 base score of 6.5 (Medium/Moderate) (GitHub Advisory, Red Hat Bugzilla).

The root cause is an integer overflow or wraparound (CWE-190) in ImageMagick's SIXEL image format decoder. When processing a specially crafted SIXEL image, an arithmetic calculation in the decoder produces a value that overflows the integer type, resulting in an out-of-bounds write to memory. The attack vector is network-based with high attack complexity, requires no privileges or user interaction, and is triggered simply by supplying a malicious image to any application that processes it with ImageMagick. No public proof-of-concept exploit code has been identified at this time (GitHub Advisory, Red Hat Bugzilla).

Successful exploitation can result in a Denial of Service (DoS) by crashing the affected application, and potentially information disclosure through memory exposure caused by the out-of-bounds write condition. The integrity impact is rated low, as the memory corruption may allow limited data modification, while availability impact is rated high due to the likelihood of application crashes. Any service or pipeline that automatically processes untrusted images using a vulnerable ImageMagick version is at risk, including web applications, media processing services, and CI/CD pipelines (GitHub Advisory, Red Hat Bugzilla).

1. Reconnaissance: Identify applications or services that accept image uploads or process remote images using ImageMagick versions prior to 7.1.2-16 (or Magick.NET prior to 14.10.4).
2. Craft malicious SIXEL image: Create a specially crafted SIXEL-format image file designed to trigger an integer overflow in the SIXEL decoder — specifically by encoding image dimensions or color parameters that cause arithmetic wraparound during buffer size calculations.
3. Deliver the payload: Submit the crafted image to the target application via an upload endpoint, API, or any mechanism that causes ImageMagick to process the file (e.g., thumbnail generation, format conversion).
4. Trigger out-of-bounds write: When ImageMagick's SIXEL decoder processes the malicious image, the integer overflow causes an out-of-bounds memory write, potentially crashing the application (DoS) or corrupting adjacent memory regions in a way that may leak information (GitHub Advisory).

• Logs: Unexpected application crashes or segmentation faults in services invoking ImageMagick; error log entries referencing SIXEL decoding failures or memory access violations.
• Process: ImageMagick worker processes (convert, magick, or application-embedded equivalents) terminating abnormally or with non-zero exit codes when processing uploaded or fetched images.
• File System: Presence of unusual .six or .sixel image files in upload directories or temporary processing folders from untrusted sources.
• Network: Repeated submission of SIXEL-format images (identifiable by the Esc P DCS sequence header) to image processing endpoints, particularly from external or unexpected IP addresses.

The vulnerability is fixed in ImageMagick 7.1.2-16 and Magick.NET 14.10.4; organizations should upgrade to these versions or later immediately. If immediate patching is not feasible, restrict access to ImageMagick-based services, validate and sanitize image files from untrusted sources before processing, and consider blocking or rejecting SIXEL-format images at the application layer. Downstream Linux distribution patches have been issued for Debian (DSA-6169-1), SUSE/openSUSE, and Amazon Linux 2 (ALAS2-2026-3220) (GitHub Advisory, Red Hat Bugzilla).

The vulnerability was disclosed by ImageMagick maintainer dlemstra via a GitHub Security Advisory on March 9, 2026. Red Hat tracked the issue via Bugzilla and assessed it as medium severity. Multiple Linux distributions including Debian, SUSE, openSUSE, and Amazon Linux issued security advisories and updated packages in the weeks following disclosure. Security scanner vendors Tenable (Nessus) and Qualys released detection plugins shortly after the advisory was published (GitHub Advisory, Red Hat Bugzilla).