CVE-2025-31115

HIGH

XZ Utils <5.8.0 - Use After Free

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2025-31115. PoCs published by greydoubt.

AI-analyzed exploit summary This repository contains test files and scripts related to the xz library, including references to CVE-2025-31115 (threaded .xz decoder memory free issue). It includes fuzzing tests, coverage scripts, and test file generators but lacks functional exploit code.

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.

Exploits (1)

nomisec WRITEUP
by greydoubt · poc
https://github.com/greydoubt/xz

This repository contains test files and scripts related to the xz library, including references to CVE-2025-31115 (threaded .xz decoder memory free issue). It includes fuzzing tests, coverage scripts, and test file generators but lacks functional exploit code.

Classification
Writeup 90%
Attack Type
Other
Complexity
Moderate
Reliability
Theoretical
Target: xz (liblzma)
No auth needed
Prerequisites: xz library source code · fuzzing tools (lcov, genhtml)
devstral-2 · analyzed Apr 09, 2026 Full analysis →

Scores

CVSS v4 8.7
EPSS 0.0059
EPSS Percentile 43.4%
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-366 CWE-416 CWE-476 CWE-826
Status published
Products (1)
tukaani-project/xz >= 5.3.3alpha, < 5.8.1
Published Apr 03, 2025
Tracked Since Feb 18, 2026