CVE-2025-31115: CWE-366: Race Condition within a Thread in tukaani-project xz
XZ Utils provide a general-purpose data-compression library plus command-line tools. In XZ Utils 5.3.3alpha to 5.8.0, the multithreaded .xz decoder in liblzma has a bug where invalid input can at least result in a crash. The effects include heap use after free and writing to an address based on the null pointer plus an offset. Applications and libraries that use the lzma_stream_decoder_mt function are affected. The bug has been fixed in XZ Utils 5.8.1, and the fix has been committed to the v5.4, v5.6, v5.8, and master branches in the xz Git repository. No new release packages will be made from the old stable branches, but a standalone patch is available that applies to all affected releases.
AI Analysis
Technical Summary
CVE-2025-31115 is a race condition vulnerability in the multithreaded .xz decoder component (liblzma) of XZ Utils versions 5.3.3alpha through 5.8.0. When processing invalid input, the decoder may crash due to heap use after free and writing to memory addresses derived from null pointers plus offsets. This affects any application or library utilizing the lzma_stream_decoder_mt function. The issue has been addressed and fixed in version 5.8.1, with patches committed to the v5.4, v5.6, v5.8, and master branches of the xz Git repository. No new releases will be made from older stable branches, but standalone patches are available for all affected versions.
Potential Impact
The vulnerability can cause application crashes and memory corruption (heap use after free and null pointer dereference) when decoding invalid .xz input in a multithreaded context. This can lead to denial of service or potentially other undefined behaviors in affected applications. There are no known exploits in the wild at this time.
Mitigation Recommendations
A fix is available in XZ Utils version 5.8.1. Users and developers should upgrade to version 5.8.1 or later. For those unable to upgrade, standalone patches have been provided for all affected releases and should be applied. No vendor advisory indicates that no action is required or that the issue is already mitigated.
CVE-2025-31115: CWE-366: Race Condition within a Thread in tukaani-project xz
Description
XZ Utils provide a general-purpose data-compression library plus command-line tools. In XZ Utils 5.3.3alpha to 5.8.0, the multithreaded .xz decoder in liblzma has a bug where invalid input can at least result in a crash. The effects include heap use after free and writing to an address based on the null pointer plus an offset. Applications and libraries that use the lzma_stream_decoder_mt function are affected. The bug has been fixed in XZ Utils 5.8.1, and the fix has been committed to the v5.4, v5.6, v5.8, and master branches in the xz Git repository. No new release packages will be made from the old stable branches, but a standalone patch is available that applies to all affected releases.
CVSS v4.0
Score 8.7high
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2025-31115 is a race condition vulnerability in the multithreaded .xz decoder component (liblzma) of XZ Utils versions 5.3.3alpha through 5.8.0. When processing invalid input, the decoder may crash due to heap use after free and writing to memory addresses derived from null pointers plus offsets. This affects any application or library utilizing the lzma_stream_decoder_mt function. The issue has been addressed and fixed in version 5.8.1, with patches committed to the v5.4, v5.6, v5.8, and master branches of the xz Git repository. No new releases will be made from older stable branches, but standalone patches are available for all affected versions.
Potential Impact
The vulnerability can cause application crashes and memory corruption (heap use after free and null pointer dereference) when decoding invalid .xz input in a multithreaded context. This can lead to denial of service or potentially other undefined behaviors in affected applications. There are no known exploits in the wild at this time.
Mitigation Recommendations
A fix is available in XZ Utils version 5.8.1. Users and developers should upgrade to version 5.8.1 or later. For those unable to upgrade, standalone patches have been provided for all affected releases and should be applied. No vendor advisory indicates that no action is required or that the issue is already mitigated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2025-03-26T15:04:52.624Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a031edecbff5d8610deb8b5
Added to database: 05/12/2026, 12:36:46 UTC
Last enriched: 07/15/2026, 11:16:49 UTC
Last updated: 09/10/2026, 19:36:50 UTC
Views: 99
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