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CVE-2025-66566

Fix: yawkat/lz4-java@33d180c

CVE-2025-66566 is a CWE-201 vulnerability in at.yawk.lz4:lz4-java. O3 Security confirms whether CVE-2025-66566 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

yawkat LZ4 Java has a possible information leak in Java safe decompressor

Also known asGHSA-cmp6-m4wj-q63q
Published
Dec 5, 2025
Updated
Jul 15, 2026
Affected
4 pkgs
Patched
1 / 4
Exploits
None indexed
Exploitation data as of Jul 15, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

4 pkgs affected
at.yawk.lz4:lz4-javaorg.lz4:lz4-javaorg.lz4:lz4-pure-javanet.jpountz.lz4:lz4

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

4 total 1 fixed
EcosystemPackageVulnerable rangeFix
Mavenat.yawk.lz4:lz4-javaall versions1.10.1
Mavenorg.lz4:lz4-javaall versionsNo fix
Mavenorg.lz4:lz4-pure-javaall versionsNo fix
Mavennet.jpountz.lz4:lz4all versionsNo fix

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for at.yawk.lz4:lz4-java. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update at.yawk.lz4:lz4-java to 1.10.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66566 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether CVE-2025-66566 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2025-66566. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

Is CVE-2025-66566 in your dependencies?

O3 detects CVE-2025-66566 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

CVE-2025-66566: lz4-java | O3 Security