---
id: CVE-2026-34743
title: >-
  XZ Utils provide a general-purpose data-compression library plus command-line
  tools
summary: >-
  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
  wher…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-122
  - CWE-131
vendor: tukaani
product: xz
affected:
  - xz < 5.8.3
patched:
  - xz 5.8.3
published: '2026-04-02'
updated: '2026-07-21'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-34743'
references:
  - url: >-
      https://github.com/tukaani-project/xz/commit/c8c22869e780ff57c96b46939c3d79ff99395f87
    label: security-advisories@github.com
  - url: 'https://github.com/tukaani-project/xz/releases/tag/v5.8.3'
    label: security-advisories@github.com
  - url: >-
      https://github.com/tukaani-project/xz/security/advisories/GHSA-x872-m794-cxhv
    label: security-advisories@github.com
  - url: 'http://www.openwall.com/lists/oss-security/2026/03/31/13'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2026/07/msg00034.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34743.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-34743'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2454589'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-34743'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-34743'
  - url: 'https://access.redhat.com/errata/RHSA-2026:64787'
  - url: 'https://access.redhat.com/errata/RHSA-2026:7647'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
epss: 0.00573
epssPercentile: 0.44927
ingestedAt: '2026-07-21T23:55:35.214Z'
---

## Overview

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.

## Affected

- `xz < 5.8.3`

## Remediation

Upgrade past the affected range:

- `xz 5.8.3`

## Vendor advisories

- **RHSA-2026:64787** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64787)
- **RHSA-2026:7647** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-04-11 · [advisory](https://access.redhat.com/errata/RHSA-2026:7647)
- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat OpenShift Container Platform 4, … · updated 2026-09-11 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34743.json)