---
id: CVE-2025-31115
title: XZ has a heap-use-after-free bug in threaded .xz decoder
summary: >-
  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 incl…
severity: high
cvss: 8.7
cvssVector: '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'
cvssSource: cna
cwe:
  - CWE-366
  - CWE-416
  - CWE-476
  - CWE-826
vendor: tukaani-project
product: xz
affected:
  - 'xz >= 5.3.3alpha, < 5.8.1'
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2025-04-03T17:57:35.541572Z'
published: '2025-04-03'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T01:06:00.051Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2025-31115'
references:
  - url: >-
      https://github.com/tukaani-project/xz/security/advisories/GHSA-6cc8-p5mm-29w2
    label: >-
      https://github.com/tukaani-project/xz/security/advisories/GHSA-6cc8-p5mm-29w2
  - url: >-
      https://github.com/tukaani-project/xz/commit/d5a2ffe41bb77b918a8c96084885d4dbe4bf6480
    label: >-
      https://github.com/tukaani-project/xz/commit/d5a2ffe41bb77b918a8c96084885d4dbe4bf6480
  - url: 'https://tukaani.org/xz/xz-cve-2025-31115.patch'
    label: 'https://tukaani.org/xz/xz-cve-2025-31115.patch'
tags:
  - cve.org
epss: 0.00675
epssPercentile: 0.52008
ingestedAt: '2026-10-15T05:52:46.100Z'
---

## Overview

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.

## Affected

- `xz >= 5.3.3alpha, < 5.8.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.