CVE-2026-32829 — lz4_flex: Decompression can leak information from uninitialized memory or reused output buffer

Affected: PSeitz lz4_flex, Red Hat Logging Subsystem for Red Hat OpenShift 6.2, Red Hat Logging Subsystem for Red Hat OpenShift 6.4, Red Hat Logging Subsystem for Red Hat OpenShift 6.5, Red Hat OpenShift AI 3.3, Red Hat OpenShift Lightspeed, Red Hat Ansible Automation Platform 2, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9, Red Hat OpenShift AI (RHOAI)

lz4_flex is a pure Rust implementation of LZ4 compression/decompression. In versions 0.11.5 and below, and 0.12.0, decompressing invalid LZ4 data can leak sensitive information from uninitialized memory or from previous decompression operations. The library fails to properly validate offset values during LZ4 "match copy operations," allowing out-of-bounds reads from the output buffer. The block-based API functions (`decompress_into`, `decompress_into_with_dict`, and others when `safe-decode` is disabled) are affected, while all frame APIs are unaffected. The impact is potential exposure of sensitive data and secrets through crafted or malformed LZ4 input. This issue has been fixed in versions 0.11.6 and 0.12.1.

GHSA-vvp9-7p8x-rfvv — lz4_flex's decompression can leak information from uninitialized memory or reused output buffer

Affected: crates.io: lz4_flex

### Summary Decompressing invalid LZ4 data can leak data from uninitialized memory, or can leak content from previous decompression operations when reusing an output buffer.

### Details The LZ4 block format defines a "match copy operation" which duplicates previously written data or data from the user-supplied dict. The position of that data is defined by an _offset_. The data is copied within the output buffer from the _offset_ to the current output position. However, lz4_flex did not properly detect invalid and out-of-bounds _offset_ values properly, causing it to copy uninitialized data from the output buffer.

Only the block based API functions are affected: `lz4_flex::block::{decompress_into, decompress_into_with_dict}`

When safe-decode is disabled _additionally_ these functions are affected `lz4_flex::block::{decompress, decompress_with_dict, decompress_size_prepended, decompress_size_prepended_with_dict}`

All `frame` APIs are _not_ affected.

There are two affected use cases: - decompressing LZ4 data with the `unsafe` implementation (`safe-decode` feature flag disabled, which is enabled by default): can leak content of uninitialized memory as decompressed result - decompressing LZ4 data into a reused, user-supplied `output` buffer (affects the `safe-decode` feature as well): can leak the previous contents of the output buffer as decompressed result

### Impact Leakage of data from uninitialized memory or content from previous decompression operations, possibly rev…

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CVE-2026-32829 — lz4_flex: Decompression can leak information from uninitialized memory or reused output buffer

GHSA-vvp9-7p8x-rfvv — lz4_flex's decompression can leak information from uninitialized memory or reused output buffer