CVE-2020-12268
📋 TL;DR
CVE-2020-12268 is a critical heap-based buffer overflow vulnerability in jbig2dec's image composition function. Attackers can exploit this to execute arbitrary code or cause denial of service by processing malicious JBIG2 image files. This affects any system or application using vulnerable versions of jbig2dec library to decode JBIG2 images.
💻 Affected Systems
- Artifex jbig2dec
- Applications using jbig2dec library (PDF viewers, document processors, image converters)
📦 What is this software?
Jbig2dec by Artifex
Leap by Opensuse
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with system-level privileges leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Application crash (denial of service) or limited code execution within the application context.
If Mitigated
Application crash with no code execution if memory protections like ASLR are effective.
🎯 Exploit Status
Proof-of-concept available through OSS-Fuzz. Exploitation requires feeding a malicious JBIG2 image to vulnerable software.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.18 and later
Vendor Advisory: https://github.com/ArtifexSoftware/jbig2dec/commit/0726320a4b55078e9d8deb590e477d598b3da66e
Restart Required: Yes
Instructions:
1. Update jbig2dec to version 0.18 or later. 2. For Linux distributions: Use package manager (apt-get upgrade jbig2dec, yum update jbig2dec). 3. For embedded systems: Recompile applications with patched library. 4. Restart affected services.
🔧 Temporary Workarounds
Disable JBIG2 image processing
allConfigure applications to disable JBIG2 image decoding if not required.
Application-specific configuration - check documentation
Input validation and sanitization
allImplement file type validation to reject or sanitize JBIG2 images from untrusted sources.
🧯 If You Can't Patch
- Implement network segmentation to isolate systems processing JBIG2 images
- Deploy application allowlisting to prevent execution of unknown binaries
🔍 How to Verify
Check if Vulnerable:
Check jbig2dec version: jbig2dec --version. If version is below 0.18, system is vulnerable.Check Version:
jbig2dec --versionVerify Fix Applied:
Verify jbig2dec version is 0.18 or higher: jbig2dec --version | grep -q '0\.1[89]\|0\.[2-9]' && echo 'Patched'📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults in jbig2dec functions
- Memory corruption errors in application logs
Network Indicators:
- Unexpected JBIG2 file transfers to vulnerable systems
- Exploit kit traffic patterns
SIEM Query:
source="application.log" AND ("segmentation fault" OR "heap overflow" OR "jbig2")🔗 References
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00034.html
- https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=20332
- https://github.com/ArtifexSoftware/jbig2dec/commit/0726320a4b55078e9d8deb590e477d598b3da66e
- https://github.com/ArtifexSoftware/jbig2dec/compare/0.17...0.18
- https://lists.debian.org/debian-lts-announce/2021/10/msg00023.html
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00034.html
- https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=20332
- https://github.com/ArtifexSoftware/jbig2dec/commit/0726320a4b55078e9d8deb590e477d598b3da66e
- https://github.com/ArtifexSoftware/jbig2dec/compare/0.17...0.18
- https://lists.debian.org/debian-lts-announce/2021/10/msg00023.html
