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CVE-2026-32829 — lz4_flex

Fix: PSeitz/lz4_flex@055502e

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

Also known asGHSA-vvp9-7p8x-rfvvRUSTSEC-2026-0041
Published
Mar 20, 2026
Updated
Sep 6, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Sep 18, 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 CVE-2026-32829.

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

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.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iolz4_flexall versions0.11.6cargo update -p lz4_flex --precise 0.11.6
🦀crates.iolz4_flex≥ 0.12.0&&< 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 CVE-2026-32829 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 CVE-2026-32829 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-32829. 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

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 se
O3 Security · Impact-Aware SCA

Is CVE-2026-32829 in your dependencies?

O3 Security finds CVE-2026-32829 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works
CVE-2026-32829: lz4_flex Memory Corruption | O3 Security