tukaani-project xz up to 5.8.2 Compression lzma_index_decoder heap-based overflow

Summaryinfo

A vulnerability described as critical has been identified in tukaani-project xz up to 5.8.2. Affected is the function lzma_index_decoder of the component Compression Handler. Executing a manipulation can lead to heap-based overflow. The identification of this vulnerability is CVE-2026-34743. The attack may be launched remotely. There is no exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as critical was found in tukaani-project xz up to 5.8.2. This vulnerability affects the function lzma_index_decoder of the component Compression Handler. The manipulation with an unknown input leads to a heap-based overflow vulnerability. The CWE definition for the vulnerability is CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). As an impact it is known to affect availability. CVE summarizes:

XZ Utils provide a general-purpose data-compression library plus command-line tools. Prior to version 5.8.3, if lzma_index_decoder() was used to decode an Index that contained no Records, the resulting lzma_index was left in a state where where a subsequent lzma_index_append() would allocate too little memory, and a buffer overflow would occur. This issue has been patched in version 5.8.3.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-34743 since 03/30/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available.

Upgrading to version 5.8.3 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch c8c22869e780ff57c96b46939c3d79ff99395f87 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Project Management Software

Vendor

• tukaani-project

Name

• xz

Version

• 5.8.0
• 5.8.1
• 5.8.2

License

• open-source

Website

• Product: https://github.com/tukaani-project/xz/

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