CVE-2020-27844: Openjpeg Buffer Overflow Vulnerability

CVE-2020-27844 Overview

A critical out-of-bounds write vulnerability has been identified in OpenJPEG's src/lib/openjp2/t2.c file affecting versions prior to 2.4.0. This flaw allows an attacker to provide specially crafted input to OpenJPEG during conversion and encoding operations, triggering an out-of-bounds write condition. Successful exploitation of this vulnerability poses significant threats to confidentiality, integrity, and system availability.

Critical Impact

This out-of-bounds write vulnerability in OpenJPEG can lead to arbitrary code execution, data corruption, or system crashes when processing malicious JPEG 2000 files.

Affected Products

• UCLouvain OpenJPEG (versions prior to 2.4.0)
• Debian Linux 9.0
• Oracle Outside In Technology 8.5.5

Discovery Timeline

• 2021-01-05 - CVE CVE-2020-27844 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-27844

Vulnerability Analysis

The vulnerability resides in the tier-2 coding component (t2.c) of the OpenJPEG library, which handles the organization and coding of compressed image data into packets. When processing specially crafted JPEG 2000 images, the library fails to properly validate input boundaries during conversion and encoding operations. This improper input validation (CWE-20) allows memory to be written beyond the allocated buffer boundaries, leading to an out-of-bounds write condition.

The local attack vector requires user interaction, as a victim must open or process a malicious JPEG 2000 file. However, once triggered, the impact is severe—affecting confidentiality through potential information disclosure, integrity through memory corruption, and availability through potential system crashes or denial of service.

Root Cause

The root cause of this vulnerability is improper input validation in the t2.c source file. The OpenJPEG library does not adequately verify the bounds of input data during JPEG 2000 conversion and encoding operations. When processing malformed or crafted image files, the tier-2 encoding routines may write data beyond allocated buffer boundaries, causing memory corruption.

Attack Vector

This vulnerability is exploited locally and requires user interaction. An attacker must craft a malicious JPEG 2000 file and convince a victim to open it with an application using the vulnerable OpenJPEG library. Common attack scenarios include:

• Embedding malicious JP2/J2K files in documents or web pages
• Distributing malicious image files via email attachments
• Hosting crafted images on websites that trigger automatic processing
• Targeting applications that automatically process uploaded images

When the vulnerable OpenJPEG library processes the malicious file, the out-of-bounds write occurs, potentially allowing the attacker to execute arbitrary code with the privileges of the victim user or cause the application to crash.

Detection Methods for CVE-2020-27844

Indicators of Compromise

• Unexpected crashes in applications using OpenJPEG when processing JPEG 2000 files
• Suspicious JP2, J2K, or JPX files with malformed headers or unusual structure
• Memory corruption errors or segmentation faults in image processing workflows
• Abnormal application behavior following JPEG 2000 file processing

Detection Strategies

• Monitor for crashes or exceptions in applications utilizing the OpenJPEG library
• Implement file integrity monitoring on systems processing untrusted JPEG 2000 images
• Deploy application-level sandboxing to isolate image processing operations
• Use memory corruption detection tools to identify out-of-bounds write attempts

Monitoring Recommendations

• Enable crash reporting and logging for applications using OpenJPEG
• Monitor system logs for signs of exploitation attempts or unusual image processing activity
• Implement network monitoring to detect potentially malicious JPEG 2000 files entering the environment
• Track OpenJPEG library versions across all systems to identify vulnerable installations

How to Mitigate CVE-2020-27844

Immediate Actions Required

• Upgrade OpenJPEG to version 2.4.0 or later immediately
• Identify all applications and systems using vulnerable versions of OpenJPEG
• Restrict processing of untrusted JPEG 2000 files until patches are applied
• Enable additional security controls on systems that must process untrusted images

Patch Information

The vulnerability has been addressed in OpenJPEG version 2.4.0. Organizations should update to this version or later to remediate the vulnerability. Multiple vendors have released security advisories and patches:

• Red Hat Bug Report #1907521 provides tracking and patch information
• Debian LTS Announcement February 2021 contains backported fixes for Debian 9
• Gentoo GLSA 202101-29 provides Gentoo-specific remediation guidance
• Oracle CPU April 2021 Security Alert addresses Outside In Technology
• Oracle CPU July 2021 Security Alert provides additional Oracle product updates

Workarounds

• Avoid processing JPEG 2000 files from untrusted sources until patches are applied
• Implement application sandboxing to limit the impact of potential exploitation
• Use alternative image formats when possible to reduce exposure
• Deploy endpoint protection solutions that can detect memory corruption attacks

# Check OpenJPEG version on Linux systems
opj_decompress -h 2>&1 | grep -i version

# Update OpenJPEG on Debian/Ubuntu
sudo apt-get update && sudo apt-get install libopenjp2-7

# Update OpenJPEG on RHEL/CentOS
sudo yum update openjpeg2