CVE-2020-6851

Q: What is the severity of CVE-2020-6851?

CVE-2020-6851 has a CVSS score of 7.5 (HIGH). This vulnerability in OpenJPEG allows attackers to execute arbitrary code or cause denial of service via a heap-based buffer overflow when processing specially crafted JPEG 2000 images. It affects systems using OpenJPEG for image processing, particularly web applications, document management systems, and media processing tools. The lack of proper validation in opj_j2k_update_image_dimensions enables this exploit.

7.5 HIGH

Denial of Service Buffer Overflow

📋 TL;DR

This vulnerability in OpenJPEG allows attackers to execute arbitrary code or cause denial of service via a heap-based buffer overflow when processing specially crafted JPEG 2000 images. It affects systems using OpenJPEG for image processing, particularly web applications, document management systems, and media processing tools. The lack of proper validation in opj_j2k_update_image_dimensions enables this exploit.

💻 Affected Systems

Products:

OpenJPEG
Applications using OpenJPEG library
ImageMagick (when compiled with OpenJPEG)
GIMP (when using OpenJPEG plugin)
Various Linux distributions' packages

Versions: OpenJPEG through version 2.3.1

Operating Systems: Linux, Windows, macOS, BSD variants

Default Config Vulnerable: ⚠️ Yes

Notes: Any application using OpenJPEG to process JPEG 2000 (.jp2, .j2k) files is vulnerable. The vulnerability is in the core library, so all configurations using affected versions are at risk.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise, data theft, or ransomware deployment.

🟠

Likely Case

Application crash causing denial of service, potentially disrupting image processing services.

🟢

If Mitigated

Limited impact with proper input validation and memory protections, potentially just crashes.

🌐 Internet-Facing: HIGH - Web applications processing user-uploaded images are directly exposed.

🏢 Internal Only: MEDIUM - Internal systems processing JPEG 2000 images could be exploited via malicious files.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ⚠️ Yes

Complexity: LOW

Proof-of-concept code exists in the GitHub issue. Exploitation requires only a malicious JPEG 2000 file, making it straightforward for attackers.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: OpenJPEG 2.3.2 and later

Vendor Advisory: https://github.com/uclouvain/openjpeg/issues/1228

Restart Required: Yes

Instructions:

1. Update OpenJPEG to version 2.3.2 or later. 2. For Linux distributions, use package manager: 'sudo apt update && sudo apt upgrade libopenjp2-7' (Debian/Ubuntu) or 'sudo yum update openjpeg2' (RHEL/CentOS). 3. Rebuild any applications statically linked to OpenJPEG. 4. Restart affected services.

🔧 Temporary Workarounds

Disable JPEG 2000 processing

all

Temporarily disable JPEG 2000 file processing in applications until patched.

# For ImageMagick: disable JP2 format in policy.xml
# For web apps: block .jp2/.j2k uploads

Input validation filtering

all

Implement strict file type validation to reject JPEG 2000 files at application boundaries.

# Example for web server: add to .htaccess
RewriteRule \.(jp2|j2k)$ - [F]

🧯 If You Can't Patch

Implement network segmentation to isolate vulnerable systems from untrusted networks.
Deploy application firewalls with file type filtering to block JPEG 2000 files.

🔍 How to Verify

Check if Vulnerable:

Check OpenJPEG version: 'opj_decompress -v' or 'dpkg -l | grep openjpeg' or 'rpm -qa | grep openjpeg'. If version is 2.3.1 or earlier, system is vulnerable.

Check Version:

opj_decompress -v 2>&1 | head -1

Verify Fix Applied:

Confirm version is 2.3.2 or later using same commands. Test with known safe JPEG 2000 files to ensure processing works.

📡 Detection & Monitoring

Log Indicators:

Application crashes with segmentation faults in OpenJPEG functions
Memory corruption errors in system logs
Failed image processing operations

Network Indicators:

Unusual uploads of JPEG 2000 files to web applications
Traffic patterns suggesting file upload exploitation attempts

SIEM Query:

source="application.log" AND ("segmentation fault" OR "heap overflow" OR "opj_")

📊 Metadata

CVE ID: CVE-2020-6851

CVSS v3 Score: 7.5 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE: CWE-787

Published: January 13, 2020

Last Updated: November 21, 2024

🔗 References

https://access.redhat.com/errata/RHSA-2020:0262 Third Party Advisory
https://access.redhat.com/errata/RHSA-2020:0274 Third Party Advisory
https://access.redhat.com/errata/RHSA-2020:0296 Third Party Advisory
https://github.com/uclouvain/openjpeg/issues/1228 Exploit,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/01/msg00025.html Mailing List,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/07/msg00008.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LACIIDDCKZJEPKTTFILSOSBQL7L3FC6V/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XBRMI2D3XPVWKE3V52KRBW7BJVLS5LD3/
https://www.debian.org/security/2021/dsa-4882 Third Party Advisory
https://www.oracle.com/security-alerts/cpujul2020.html Patch,Third Party Advisory
https://access.redhat.com/errata/RHSA-2020:0262 Third Party Advisory
https://access.redhat.com/errata/RHSA-2020:0274 Third Party Advisory
https://access.redhat.com/errata/RHSA-2020:0296 Third Party Advisory
https://github.com/uclouvain/openjpeg/issues/1228 Exploit,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/01/msg00025.html Mailing List,Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/07/msg00008.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LACIIDDCKZJEPKTTFILSOSBQL7L3FC6V/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XBRMI2D3XPVWKE3V52KRBW7BJVLS5LD3/
https://www.debian.org/security/2021/dsa-4882 Third Party Advisory
https://www.oracle.com/security-alerts/cpujul2020.html Patch,Third Party Advisory

📋 TL;DR

💻 Affected Systems

📦 What is this software?

Debian Linux by Debian

Debian Linux by Debian

Debian Linux by Debian

Enterprise Linux by Redhat

Enterprise Linux Desktop by Redhat

Enterprise Linux Eus by Redhat

Enterprise Linux Eus by Redhat

Enterprise Linux Eus by Redhat

Enterprise Linux Eus by Redhat

Enterprise Linux Server by Redhat

Enterprise Linux Server Aus by Redhat

Enterprise Linux Server Aus by Redhat

Enterprise Linux Server Aus by Redhat

Enterprise Linux Server Tus by Redhat

Enterprise Linux Server Tus by Redhat

Enterprise Linux Server Tus by Redhat

Enterprise Linux Workstation by Redhat

Fedora by Fedoraproject

Fedora by Fedoraproject

Georaster by Oracle

Openjpeg by Uclouvain

Outside In Technology by Oracle

Outside In Technology by Oracle

⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Disable JPEG 2000 processing

Input validation filtering

🧯 If You Can't Patch

🔍 How to Verify

Check if Vulnerable:

Check Version:

Verify Fix Applied:

📡 Detection & Monitoring

Log Indicators:

Network Indicators:

SIEM Query:

📊 Metadata

🔗 References

📤 Share & Export

🔗 Related Vulnerabilities