Overview
CVE-2025-66566 is a vulnerability affecting the Java-based decompressor implementations within the yawkat LZ4 Java library (lz4-java) version 1.10.0 and earlier. This flaw stems from insufficient clearing of the output buffer, potentially allowing remote attackers to read previous buffer contents through crafted compressed input. In scenarios where the output buffer is reused without being properly cleared, this could result in the disclosure of sensitive data. This vulnerability has been addressed in version 1.10.1.
Technical Details
The vulnerability lies in the Java implementation of the LZ4 decompressor within the lz4-java library. Due to inadequate clearing of the output buffer after a decompression operation, subsequent decompression operations might inadvertently expose fragments of previously decompressed data. This can be exploited by a remote attacker who provides specially crafted compressed input designed to trigger this behavior. It’s crucial to note that JNI-based implementations of the LZ4 decompressor are not affected by this vulnerability.
CVSS Analysis
Currently, a CVSS score has not been assigned to CVE-2025-66566. However, the potential for sensitive data exposure warrants serious consideration. Given the possible impact on data confidentiality, a thorough risk assessment is advised.
Possible Impact
The impact of CVE-2025-66566 can be significant, especially in applications that handle sensitive data such as:
- Applications storing and processing personally identifiable information (PII)
- Systems handling financial data (e.g., credit card numbers, bank account details)
- Applications dealing with confidential business information (e.g., trade secrets, contracts)
An attacker could potentially exploit this vulnerability to gain unauthorized access to this sensitive information, leading to data breaches, financial losses, and reputational damage.
Mitigation and Patch Steps
The recommended mitigation is to upgrade to lz4-java version 1.10.1 or later. This version includes a fix that properly clears the output buffer, preventing the exposure of sensitive data. Follow these steps:
- Identify Affected Systems: Determine which applications and systems are using lz4-java version 1.10.0 or earlier.
- Upgrade lz4-java: Update the lz4-java dependency in your project to version 1.10.1 or later. This typically involves updating your project’s dependency management configuration (e.g., Maven, Gradle).
- Verify the Upgrade: After upgrading, thoroughly test your application to ensure that the vulnerability is no longer present and that the LZ4 decompression functionality is working as expected.
- Monitor for Anomalies: Continuously monitor your systems for any suspicious activity that might indicate an attempted exploitation of this vulnerability.
References
- Commit fixing the vulnerability: https://github.com/yawkat/lz4-java/commit/33d180cb70c4d93c80fb0dc3ab3002f457e93840
- GitHub Security Advisory: https://github.com/yawkat/lz4-java/security/advisories/GHSA-cmp6-m4wj-q63q
