CVE-2025-12183: LZ4 Java Library DoS Vulnerability

CVE-2025-12183 Overview

Out-of-bounds memory operations in org.lz4:lz4-java version 1.8.0 and earlier allow remote attackers to cause denial of service and read adjacent memory via untrusted compressed input. This vulnerability (CWE-125: Out-of-bounds Read) affects applications that process untrusted LZ4-compressed data, potentially exposing sensitive information from adjacent memory regions while also enabling service disruption.

Critical Impact

Remote attackers can exploit this vulnerability to crash applications processing malicious LZ4 data and potentially leak sensitive information from memory, affecting availability and confidentiality of affected systems.

Affected Products

• org.lz4:lz4-java version 1.8.0 and earlier

Discovery Timeline

• 2025-11-28 - CVE-2025-12183 published to NVD
• 2025-12-29 - Last updated in NVD database

Technical Details for CVE-2025-12183

Vulnerability Analysis

This out-of-bounds read vulnerability exists in the lz4-java library, a Java binding for the high-performance LZ4 compression algorithm. The flaw allows attackers to craft malicious compressed input that causes the decompression routine to read beyond allocated buffer boundaries.

When processing specially crafted compressed data, the library fails to properly validate offset and length parameters during decompression operations. This improper bounds checking allows memory access outside the intended buffer, which can result in two primary impacts: reading sensitive data from adjacent memory regions (information disclosure) and causing application crashes when invalid memory is accessed (denial of service).

The vulnerability is particularly concerning because LZ4 is commonly used in high-performance scenarios such as database systems, message queues, and data pipelines where untrusted data may be processed.

Root Cause

The root cause is insufficient validation of decompression parameters when handling untrusted compressed input. The library does not adequately verify that offset and length values embedded in the compressed data stream will result in memory operations that remain within allocated buffer boundaries. This allows maliciously crafted LZ4-compressed payloads to trigger out-of-bounds memory reads during the decompression process.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by sending specially crafted LZ4-compressed data to any application using the vulnerable library versions. When the target application attempts to decompress this malicious input, the out-of-bounds read occurs.

The vulnerability can be exploited in any scenario where:

• An application accepts LZ4-compressed data from untrusted sources
• The compressed data is processed without prior validation
• Network services, APIs, or file processing pipelines use the vulnerable library

Exploitation results in potential information disclosure from adjacent memory regions and denial of service through application crashes.

Detection Methods for CVE-2025-12183

Indicators of Compromise

• Unexpected application crashes or exceptions during LZ4 decompression operations
• Unusual memory access patterns or segmentation faults in Java applications using lz4-java
• Anomalous network traffic containing malformed LZ4-compressed payloads
• Error logs indicating ArrayIndexOutOfBoundsException or similar memory access violations in decompression code paths

Detection Strategies

• Implement dependency scanning to identify applications using org.lz4:lz4-java versions 1.8.0 or earlier
• Monitor application logs for decompression-related exceptions and memory access errors
• Deploy runtime application self-protection (RASP) to detect anomalous memory access patterns
• Use network intrusion detection systems to identify potentially malicious compressed data payloads

Monitoring Recommendations

• Enable verbose logging for applications processing LZ4-compressed data from untrusted sources
• Set up alerting for unusual crash patterns or memory-related exceptions in affected applications
• Monitor application performance metrics for signs of denial of service attempts
• Track dependency versions in CI/CD pipelines to ensure vulnerable library versions are flagged

How to Mitigate CVE-2025-12183

Immediate Actions Required

• Upgrade org.lz4:lz4-java to version 1.8.1 or later immediately
• Audit all applications to identify usage of vulnerable library versions
• Implement input validation for any compressed data received from untrusted sources
• Consider temporarily disabling LZ4 decompression functionality for untrusted input until patches are applied

Patch Information

The vulnerability has been addressed in lz4-java version 1.8.1. The fix implements proper bounds checking during decompression operations to prevent out-of-bounds memory reads.

For detailed patch information, see the GitHub Release v1.8.1.

Additional security guidance is available from the Sonatype Security Advisory and the Openwall OSS Security Discussion.

Workarounds

• Avoid processing LZ4-compressed data from untrusted sources until the library is updated
• Implement application-level size and bounds validation before passing data to the decompression functions
• Use network segmentation to limit exposure of vulnerable services to untrusted networks
• Deploy web application firewalls (WAF) or API gateways to filter potentially malicious compressed payloads

# Maven dependency update example
# Update pom.xml to use patched version:
# <dependency>
#     <groupId>org.lz4</groupId>
#     <artifactId>lz4-java</artifactId>
#     <version>1.8.1</version>
# </dependency>

# Verify current version in your project
mvn dependency:tree -Dincludes=org.lz4:lz4-java

# Force update to latest version
mvn versions:use-latest-versions -Dincludes=org.lz4:lz4-java