---
id: CVE-2026-117610
title: libexpat through 2.9.0 NULL Pointer Dereference via External Entity Subparser
summary: >-
  libexpat through 2.9.0 contains a NULL pointer dereference vulnerability in
  externalEntityInitProcessor2() in lib/xmlparse.c that mishandles the
  XML_TOK_NONE token from empty input. Attackers who control stream chunking can
  force an empt…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-476
vendor: libexpat
product: libexpat
affected:
  - libexpat <= 2.9.0
published: '2026-10-28'
updated: '2026-10-28'
sourceUpdated: '2026-10-28T02:03:18.766Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-117610'
references:
  - url: 'https://github.com/libexpat/libexpat/pull/1444'
  - url: >-
      https://github.com/libexpat/libexpat/commit/7b0d50e4b1d16fafd55876260701e04279a7489d
  - url: >-
      https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L3468-L3510
  - url: 'https://github.com/libexpat/libexpat'
  - url: >-
      https://www.vulncheck.com/advisories/libexpat-through-2.9.0-null-pointer-dereference-via-external-entity-subparser
    label: >-
      VulnCheck Advisory: libexpat through 2.9.0 NULL Pointer Dereference via
      External Entity Subparser
tags:
  - cve.org
ingestedAt: '2026-10-28T03:02:57.626Z'
---

## Overview

libexpat through 2.9.0 contains a NULL pointer dereference vulnerability in externalEntityInitProcessor2() in lib/xmlparse.c that mishandles the XML_TOK_NONE token from empty input. Attackers who control stream chunking can force an empty non-final first parse on an external entity subparser, causing a later parse to crash the application.

## Affected

- `libexpat <= 2.9.0`

## Remediation

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