CVE-2026-32829
lz4_flex: Decompression can leak information from uninitialized memory or reused output buffer
EPSS Exploitation Probability
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.
Blast Radius
lz4_flex🦀lz4_flexReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | lz4_flex | all versions | 0.11.6 |
| 🦀crates.io | lz4_flex | ≥ 0.12.0&&< 0.12.1 | 0.12.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for lz4_flex. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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.
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.
How O3 protects you
O3 pinpoints whether CVE-2026-32829 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
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.
Frequently Asked Questions
Is CVE-2026-32829 in your dependencies?
O3 detects CVE-2026-32829 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.