CVE-2021-20310
📋 TL;DR
This CVE describes a division-by-zero vulnerability in ImageMagick's ConvertXYZToJzazbz() function in MagickCore/colorspace.c, which can be triggered by processing a specially crafted image file. It may lead to undefined behavior, such as crashes or denial of service, affecting applications that use vulnerable versions of ImageMagick to handle image files. Attackers can exploit this by submitting malicious images to target systems.
💻 Affected Systems
- ImageMagick
📦 What is this software?
Imagemagick by Imagemagick
⚠️ Risk & Real-World Impact
Worst Case
Exploitation could cause the application using ImageMagick to crash, leading to denial of service and potential system instability or downtime.
Likely Case
Most probable impact is application crashes or denial of service when processing malicious images, disrupting services that rely on ImageMagick for image manipulation.
If Mitigated
With proper controls like input validation and patching, the risk is reduced to minimal, with no significant impact on system availability.
🎯 Exploit Status
Exploitation requires an attacker to submit a crafted image file, which is straightforward if the application processes untrusted images.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 7.0.11 or later
Vendor Advisory: https://bugzilla.redhat.com/show_bug.cgi?id=1946728
Restart Required: Yes
Instructions:
1. Check current ImageMagick version. 2. Update to version 7.0.11 or later using package manager (e.g., 'apt-get update && apt-get upgrade imagemagick' on Debian/Ubuntu). 3. Restart any services or applications using ImageMagick.
🔧 Temporary Workarounds
Disable Image Processing for Untrusted Sources
allConfigure applications to avoid using ImageMagick for processing untrusted image files, reducing exposure.
# Modify application configuration to restrict image processing or use alternative libraries
🧯 If You Can't Patch
- Implement strict input validation to reject or sanitize image files from untrusted sources.
- Use network segmentation and firewalls to limit access to services using ImageMagick, reducing attack surface.
🔍 How to Verify
Check if Vulnerable:
Run 'convert --version' or 'magick --version' to check the ImageMagick version; if it is below 7.0.11, the system is vulnerable.Check Version:
convert --version | head -1Verify Fix Applied:
After updating, run the version check command again to confirm the version is 7.0.11 or later.📡 Detection & Monitoring
Log Indicators:
- Look for application crashes, segmentation faults, or error logs related to ImageMagick processes when handling image files.
Network Indicators:
- Monitor for unusual spikes in image uploads or processing requests that could indicate exploitation attempts.
SIEM Query:
Example: 'source="application.log" AND ("segmentation fault" OR "ImageMagick" AND error)'