What is CVE-2026-32829?

CVE-2026-32829 is a high-severity security vulnerability in lz4_flex (rust), affecting versions < 0.11.6. It is fixed in 0.11.6, 0.12.1.

Which versions of lz4_flex are affected by CVE-2026-32829?

lz4_flex (rust) versions < 0.11.6 is affected.

Is there a fix for CVE-2026-32829?

Yes. CVE-2026-32829 is fixed in 0.11.6, 0.12.1. Upgrade to this version or later.

Is CVE-2026-32829 exploitable, and should I be worried?

Whether CVE-2026-32829 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2026-32829 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

How do I fix CVE-2026-32829?

Upgrade: lz4_flex to 0.11.6 or later, lz4_flex to 0.12.1 or later.

CVE-2026-32829 in lz4_flex

Q: Which versions of lz4_flex are affected by CVE-2026-32829?

lz4_flex (rust) versions < 0.11.6 is affected.

Q: Is there a fix for CVE-2026-32829?

Yes. CVE-2026-32829 is fixed in 0.11.6, 0.12.1. Upgrade to this version or later.

Q: Is CVE-2026-32829 exploitable, and should I be worried?

Whether CVE-2026-32829 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2026-32829 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2026-32829?

Upgrade: lz4_flex to 0.11.6 or later, lz4_flex to 0.12.1 or later.

Summary

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

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

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.

Impact

Leakage of data from uninitialized memory or content from previous decompression operations, possibly revealing sensitive information and secrets.

Affected versions

lz4_flex (< 0.11.6) lz4_flex (>= 0.12.0, < 0.12.1)

Security releases

lz4_flex → 0.11.6 (rust) lz4_flex → 0.12.1 (rust)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade the following packages to resolve this vulnerability:

lz4_flex to 0.11.6 or later; lz4_flex to 0.12.1 or later

Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.

Frequently Asked Questions

What is CVE-2026-32829? CVE-2026-32829 is a high-severity security vulnerability in lz4_flex (rust), affecting versions < 0.11.6. It is fixed in 0.11.6, 0.12.1.
Which versions of lz4_flex are affected by CVE-2026-32829? lz4_flex (rust) versions < 0.11.6 is affected.
Is there a fix for CVE-2026-32829? Yes. CVE-2026-32829 is fixed in 0.11.6, 0.12.1. Upgrade to this version or later.
Is CVE-2026-32829 exploitable, and should I be worried? Whether CVE-2026-32829 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2026-32829 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2026-32829?
- Upgrade lz4_flex to 0.11.6 or later
- Upgrade lz4_flex to 0.12.1 or later