yawkat LZ4 Java: LZ4FrameInputStream reallocates block buffers for every frame, allowing CPU and GC amplification from small inputs

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-106450: 0.45% estimated exploitation activity in the next 30 days; percentile 39.44 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary LZ4FrameInputStream allocates two new buffers of the frame's maximum block size, up to 4 MiB each, every time it reads a frame header. Because concatenated frames are read by default, an input made of many minimal empty frames forces about 8 MiB of zeroed heap allocation for every 11 input bytes. Details In net.jpountz.lz4.LZ4FrameInputStream.readHeader(): This runs for every frame, and the previous frame's arrays are never reused. A valid 11-byte frame consists of the magic number, FLG 0x60, BD 0x70 (4 MiB blocks), the header checksum, and an immediate end mark. It carries no data, yet triggers the full 8 MiB allocation. new LZ4FrameInputStream(in) reads concatenated frames by default. In local measurements on JDK 25, 10,000 such frames (110 KB of input) took about 8 seconds of CPU to read, roughly 70 seconds per MiB of input. This was similar under G1, Parallel, Serial and ZGC. A legitimate stream costs orders of magnitude less per input byte. Impact Applications that…

Published by the source

7 Oct 2026, 20:35 UTC

Last modified by the source

7 Oct 2026, 20:45 UTC

Source last checked

26 Oct 2026, 16:58 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-gm45-99xc-r7wv

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-gm45-99xc-r7wv

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# Patch Next advisory brief: CVE-2026-106450

Advisory: yawkat LZ4 Java: LZ4FrameInputStream reallocates block buffers for every frame, allowing CPU and GC amplification from small inputs
IDs: CVE-2026-106450, GHSA-gm45-99xc-r7wv
Record: https://patchnext.com/advisories/cve-2026-106450 (revision 2, source checked 26 Oct 2026, 16:58 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: at.yawk.lz4:lz4-java 1.11.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven at.yawk.lz4:lz4-java: affected <= 1.11.3; fixed in 1.11.4
- Maven org.lz4:lz4-java: affected <= 1.8.1

## Suggested inspection (read-only)
- Maven at.yawk.lz4:lz4-java: check the installed version with your package manager.
- Maven org.lz4:lz4-java: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on at.yawk.lz4:lz4-java, org.lz4:lz4-java.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-gm45-99xc-r7wv (OSV record GHSA-gm45-99xc-r7wv lists affected ranges: Maven at.yawk.lz4:lz4-java >=0 =0 <=1.8.1)
- Verified: https://github.com/advisories/GHSA-gm45-99xc-r7wv (GitHub-reviewed advisory GHSA-gm45-99xc-r7wv lists affected ranges: Maven at.yawk.lz4:lz4-java >=0 =0 <=1.8.1)

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