vulnerability / NVI-00011839 / Revision 3
yawkat LZ4 Java: LZ4FrameInputStream reallocates block buffers for every frame, allowing CPU and GC amplification from small inputs
GitHub lists this reviewed advisory for at.yawk.lz4:lz4-java, org.lz4:lz4-java. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
5.3 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
5.3 MEDIUM (3.1)
security-advisories@github.com severity; no combined Null risk score.
0.454%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.39409. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
at.yawk.lz4:lz4-java
source listed<= 1.11.3
### 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()`: ```java maxBlockSize = frameInfo.getBD().getBlockMaximumSize(); compressedBuffer = new byte[maxBlockSize]; // Reused during different compressions rawBuffer = new byte[maxBlockSize]; buffer = ByteBuffer.wrap(rawBuffer); ``` 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
org.lz4:lz4-java
source listed<= 1.8.1
### 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()`: ```java maxBlockSize = frameInfo.getBD().getBlockMaximumSize(); compressedBuffer = new byte[maxBlockSize]; // Reused during different compressions rawBuffer = new byte[maxBlockSize]; buffer = ByteBuffer.wrap(rawBuffer); ``` 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
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
- NVD lastModified does not establish freshness of every associated CPE record.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-gm45-99xc-r7wv ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-106450 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
- CVE-2026-106450 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 3 ·
Source facts changed; compare the preserved prior revision.
- Revision 2 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.