---
id: CVE-2026-86143
title: >-
  In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback
  and xmlBufUse causes negative lengths to reach write callbacks, aka a lack of
  a check for integer overflow before calling writecallback
summary: >-
  In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback
  and xmlBufUse causes negative lengths to reach write callbacks, aka a lack of
  a check for integer overflow before calling writecallback. This has security
  rele…
severity: medium
cvss: 6.9
cvssVector: 'CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L'
cwe:
  - CWE-192
  - CWE-190
vendor: xmlsoft
product: libxml2
affected:
  - libxml2 < 2.15.4
patched:
  - libxml2 2.15.4
published: '2026-09-05'
updated: '2026-09-15'
sourceUpdated: '2026-09-15T19:31:15.857'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86143'
references:
  - url: >-
      https://github.com/GNOME/libxml2/commit/90f293ba74d28b1d570920382e707586f68ebf35
    label: cve@mitre.org
  - url: 'https://github.com/GNOME/libxml2/compare/v2.15.3...v2.15.4'
    label: cve@mitre.org
  - url: 'https://gitlab.gnome.org/GNOME/libxml2/-/work_items/1111'
    label: cve@mitre.org
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-86143.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-86143'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2528987'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-86143'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86143'
  - url: 'https://access.redhat.com/errata/RHSA-2026:64463'
  - url: 'https://access.redhat.com/errata/RHSA-2026:71586'
  - url: 'https://access.redhat.com/errata/RHSA-2026:71641'
  - url: 'https://access.redhat.com/errata/RHSA-2026:71585'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00185
epssPercentile: 0.0718
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-08T18:05:53.926972Z'
ingestedAt: '2026-09-06T02:48:38.999Z'
---

## Overview

In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback and xmlBufUse causes negative lengths to reach write callbacks, aka a lack of a check for integer overflow before calling writecallback. This has security relevance for many types of uses of that length value within a callback.

## Affected

- `libxml2 < 2.15.4`

## Remediation

Upgrade past the affected range:

- `libxml2 2.15.4`

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat OpenShift Container Platform 4 · updated 2026-09-24 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-86143.json)
- **RHSA-2026:64463** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-06 · [advisory](https://access.redhat.com/errata/RHSA-2026:64463)
- **RHSA-2026:71586** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71586)
- **RHSA-2026:71641** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux BaseOS (v. 8) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71641)
- **RHSA-2026:71585** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9) · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71585)