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GHSA-vvp9-7p8x-rfvv lz4_flex

Fix: PSeitz/lz4_flex@055502e

GHSA-vvp9-7p8x-rfvv is a CWE-201 vulnerability in lz4_flex. A fix is available for lz4_flex — see the affected versions and patch details below.

lz4_flex's decompression can leak information from uninitialized memory or reused output buffer

Also known asCVE-2026-32829RUSTSEC-2026-0041
Published
Mar 16, 2026
Updated
Sep 10, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Sep 20, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-vvp9-7p8x-rfvv.

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs48th percentile — riskier than 48% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

2 pkgs affected
🦀lz4_flex🦀lz4_flex

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

Description

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 revealing sensitive information and secrets.

Mitigation

lz4_flex 0.12.1 and 0.11.6 fixes this issue without requiring changes in user code.

If you cannot upgrade, you can mitigate this vulnerability by zeroing the output buffer before calling block::decompress_into or block::decompress_into_with_dict (only block based API is affected, frame API is not affected). Additionally the the safe-decode feature flag should be enabled.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iolz4_flexall versions0.11.6cargo update -p lz4_flex --precise 0.11.6
🦀crates.iolz4_flex0.12.0&&< 0.12.10.12.1cargo update -p lz4_flex --precise 0.12.1

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for lz4_flex, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update lz4_flex to 0.11.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vvp9-7p8x-rfvv 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-vvp9-7p8x-rfvv can be triaged on real exposure rather than presence alone.

Tailored to GHSA-vvp9-7p8x-rfvv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

In RHEL 9 and RHEL 10, this vulnerability presents minimal risk as the rust-analyzer component operates in a "closed loop," strictly decompressing its own internal database. Because it does not process external or untrusted data, exploitation requires an attacker to already possess local access and sufficient…

ProductFixed inAdvisory
Logging for Red Hat OpenShift 6.2openshift-logging/vector-rhel9:1776894389RHSA-2026:11800
Logging Subsystem for Red Hat OpenShift 6.4openshift-logging/vector-rhel9:1780052069RHSA-2026:22862
Logging Subsystem for Red Hat OpenShift 6.5openshift-logging/vector-rhel9:1777574710RHSA-2026:16354
Red Hat OpenShift AI 3.3rhoai/odh-llm-d-inference-scheduler-rhel9:1778263962RHSA-2026:19712

Frequently Asked Questions

### 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 fr
O3 Security · Impact-Aware SCA

Is GHSA-vvp9-7p8x-rfvv in your dependencies?

O3 Security finds GHSA-vvp9-7p8x-rfvv across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

GHSA-vvp9-7p8x-rfvv: lz4_flex Info Disclosure | O3 Security