---
id: CVE-2026-115506
title: libexpat through 2.9.0 Denial of Service via Billion Laughs Detection Delay
summary: >-
  libexpat through 2.9.0 contains a denial of service vulnerability because
  billion laughs protection in accountingDiffTolerated() in xmlparse.c detects
  entity amplification too late. Attackers can supply a moderately sized XML
  document wi…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-776
vendor: libexpat
product: libexpat
affected:
  - libexpat <= 2.9.0
published: '2026-10-22'
updated: '2026-10-22'
sourceUpdated: '2026-10-22T19:14:06.001Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-115506'
references:
  - url: 'https://github.com/libexpat/libexpat/pull/1433'
  - url: 'https://github.com/libexpat/libexpat/issues/1160'
  - url: 'https://github.com/hannob/lololol'
  - url: 'https://github.com/libexpat/libexpat'
  - url: >-
      https://www.vulncheck.com/advisories/libexpat-through-2.9.0-denial-of-service-via-billion-laughs-detection-delay
    label: >-
      VulnCheck Advisory: libexpat through 2.9.0 Denial of Service via Billion
      Laughs Detection Delay
tags:
  - cve.org
ingestedAt: '2026-10-22T22:00:50.411Z'
---

## Overview

libexpat through 2.9.0 contains a denial of service vulnerability because billion laughs protection in accountingDiffTolerated() in xmlparse.c detects entity amplification too late. Attackers can supply a moderately sized XML document with a large DTD and nested entity expansions to consume tens of seconds of CPU per parse.

## Affected

- `libexpat <= 2.9.0`

## Remediation

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