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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
Present
Additional conditions required
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
None
No data modification
Availability
None
No disruption
CVSS Vector v4.0
Vulnerable Products 2
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Pseitz Lz4_Flex
cpe:2.3:a:pseitz:lz4_flex:*:*:*:*:*:rust:*:*
|
— |
0.11.6
|
|
Pseitz Lz4_Flex
cpe:2.3:a:pseitz:lz4_flex:0.12.0:*:*:*:*:rust:*:*
|
— | — |
References 3
https://github.com/PSeitz/lz4_flex/commit/055502ee5d297ecd6bf448ac91c055c7f6df9…
security-advisories@github.com
https://github.com/PSeitz/lz4_flex/security/advisories/GHSA-vvp9-7p8x-rfvv
security-advisories@github.com
https://rustsec.org/advisories/RUSTSEC-2026-0041.html
security-advisories@github.com