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

CVE-2025-66566 · Severity: medium · CVSS 4 · Published 2025-12-05

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.

Technologies: at.yawk.lz4:lz4-java (Maven), org.lz4:lz4-java (Maven). Vendors: Maven.

Quick answers

Is CVE-2025-66566 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-66566 being exploited in the wild.
How severe is CVE-2025-66566?
Medium severity, with a CVSS score of 4, published 5 December 2025.
Which products and versions are affected?
at.yawk.lz4:lz4-java (Maven) ECOSYSTEM:introduced=0,fixed=1.10.1; net.jpountz.lz4:lz4 (Maven) ECOSYSTEM:introduced=0,last_affected=1.8.1; org.lz4:lz4-java (Maven) ECOSYSTEM:introduced=0,last_affected=1.8.1; org.lz4:lz4-pure-java (Maven) ECOSYSTEM:introduced=0,last_affected=1.8.1.
Is there a fix for CVE-2025-66566?
Yes. at.yawk.lz4:lz4-java (Maven): upgrade to 1.10.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-66566?
Check whether you run at.yawk.lz4:lz4-java (Maven), net.jpountz.lz4:lz4 (Maven), org.lz4:lz4-java (Maven) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • at.yawk.lz4:lz4-java (Maven): upgrade to 1.10.1 or later
    # set at.yawk.lz4:lz4-java to 1.10.1 in your pom.xml or build.gradle

Affected products

  • at.yawk.lz4:lz4-java (Maven) ECOSYSTEM:introduced=0,fixed=1.10.1
  • net.jpountz.lz4:lz4 (Maven) ECOSYSTEM:introduced=0,last_affected=1.8.1
  • org.lz4:lz4-java (Maven) ECOSYSTEM:introduced=0,last_affected=1.8.1
  • org.lz4:lz4-pure-java (Maven) ECOSYSTEM:introduced=0,last_affected=1.8.1

Identifiers

  • CVE-2025-66566
  • GHSA-cmp6-m4wj-q63q

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