CVE-2021-3575: Openjpeg Buffer Overflow Vulnerability

CVE-2021-3575 Overview

A heap-based buffer overflow vulnerability was discovered in OpenJPEG, specifically in the color.c file at line 379:42 within the sycc420_to_rgb function. This vulnerability is triggered when decompressing a specially crafted .j2k (JPEG 2000) file. An attacker could exploit this flaw to execute arbitrary code with the permissions of the application compiled against the OpenJPEG library.

Critical Impact

This heap overflow vulnerability allows attackers to achieve arbitrary code execution by providing a malicious JPEG 2000 image file, potentially leading to complete system compromise with the privileges of the vulnerable application.

Affected Products

• UCLouvain OpenJPEG (all affected versions)
• Red Hat Enterprise Linux 6.0, 7.0, 8.0
• Fedora 33, 34

Discovery Timeline

• 2022-03-04 - CVE-2021-3575 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2021-3575

Vulnerability Analysis

This vulnerability (CWE-787: Out-of-bounds Write) exists in the color space conversion functionality of OpenJPEG. The sycc420_to_rgb function is responsible for converting images from the YCbCr 4:2:0 color space to RGB format during JPEG 2000 decompression. Due to improper bounds checking during this conversion process, processing a maliciously crafted .j2k file can trigger a heap-based buffer overflow.

The vulnerability requires local access and user interaction (opening a malicious file), but once triggered, it can result in complete compromise of confidentiality, integrity, and availability of the affected system. Applications that integrate OpenJPEG for image processing—including image viewers, converters, and document processors—are potentially affected.

Root Cause

The root cause of CVE-2021-3575 lies in insufficient validation of buffer boundaries in the sycc420_to_rgb function located in color.c. During the YCbCr 4:2:0 to RGB color space conversion, the function fails to properly verify that write operations remain within allocated heap memory bounds. When processing specially crafted JPEG 2000 files with malformed header data or manipulated color component dimensions, the function writes beyond the allocated buffer, corrupting adjacent heap memory.

Attack Vector

The attack vector for this vulnerability is local, requiring an attacker to convince a user to open a malicious .j2k or JPEG 2000 file. Attack scenarios include:

1. Email attachment: Sending a malicious .j2k file as an email attachment
2. Drive-by download: Hosting malicious JPEG 2000 images on websites
3. Supply chain: Embedding malicious images in documents or archives
4. File sharing: Distributing malicious images through file-sharing platforms

When a vulnerable application processes the crafted image, the heap overflow occurs during color conversion, potentially allowing the attacker to overwrite critical heap metadata or function pointers, leading to arbitrary code execution.

The vulnerability is triggered in the image decompression pipeline when the sycc420_to_rgb function processes color data. The malicious file contains specially crafted header values that cause the function to miscalculate buffer sizes, resulting in heap corruption during the color space transformation. For detailed technical analysis, refer to the GitHub Issue #1347 and the Red Hat Bug Report.

Detection Methods for CVE-2021-3575

Indicators of Compromise

• Unexpected crashes or segmentation faults in applications using OpenJPEG when processing .j2k files
• Suspicious JPEG 2000 files with anomalous header values or corrupted color component metadata
• Memory corruption errors logged by applications during image decompression operations
• Unusual process behavior following the opening of JPEG 2000 image files

Detection Strategies

• Monitor application crash reports for patterns involving OpenJPEG library components, particularly in color.c or color conversion functions
• Implement file integrity monitoring to detect suspicious .j2k or .jp2 files with unusual metadata structures
• Deploy memory protection mechanisms (ASLR, DEP/NX) to detect and mitigate exploitation attempts
• Use application sandboxing to isolate image processing operations and detect anomalous behavior

Monitoring Recommendations

• Enable heap protection and memory sanitization in development and testing environments to identify exploitation attempts
• Monitor system logs for crash dumps referencing OpenJPEG components
• Implement network-level detection for JPEG 2000 files being transferred, particularly from untrusted sources
• Review endpoint detection logs for suspicious process spawning following image file access

How to Mitigate CVE-2021-3575

Immediate Actions Required

• Update OpenJPEG to the latest patched version available from your distribution
• Apply security updates from Red Hat, Fedora, Debian, or Ubuntu as applicable to your environment
• Restrict the processing of JPEG 2000 files from untrusted sources until patches are applied
• Consider disabling automatic image preview features in applications that use OpenJPEG

Patch Information

Security patches addressing CVE-2021-3575 have been released by multiple Linux distributions. Administrators should apply updates from their respective package managers:

• Fedora: Updates available via Fedora package announcements for Fedora 33 and 34
• Red Hat Enterprise Linux: Patches available for RHEL 6.0, 7.0, and 8.0 through the Red Hat security advisory system
• Ubuntu: Security updates documented in the Ubuntu CVE-2021-3575 advisory
• Debian: Long-term support patches documented in the Debian LTS Announcement

Workarounds

• If patching is not immediately possible, consider using alternative JPEG 2000 processing libraries temporarily
• Implement strict input validation for JPEG 2000 files before processing with OpenJPEG
• Use application sandboxing (e.g., containers, seccomp profiles) to limit the impact of potential exploitation
• Disable or restrict JPEG 2000 file handling in web-facing or email-processing applications

# Example: Update OpenJPEG on Fedora/RHEL systems
sudo dnf update openjpeg2 openjpeg2-devel

# Example: Update OpenJPEG on Debian/Ubuntu systems
sudo apt update && sudo apt upgrade libopenjp2-7

# Verify installed version
opj_decompress -h 2>&1 | head -1