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Vulnerability · Published Oct 22, 2026 · Assigned by VulnCheck

CVE-2026-115506libexpat through 2.9.0 Denial of Service via Billion Laughs Detection Delay

High 7.5

In plain English

A high-severity security flaw in libexpat from libexpat. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 39% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.4%top 60.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.21expat2.10.0-r0ALPINE-CVE-2026-115506
Alpine:v3.22expat2.10.0-r0ALPINE-CVE-2026-115506
Alpine:v3.23expat2.10.0-r0ALPINE-CVE-2026-115506
Alpine:v3.24expat2.10.0-r0ALPINE-CVE-2026-115506
Debian:12expatno fix listedDEBIAN-CVE-2026-115506
Debian:13expatno fix listedDEBIAN-CVE-2026-115506
Debian:14expatno fix listedDEBIAN-CVE-2026-115506
Ubuntu:22.04:LTScadaverno fix listedUBUNTU-CVE-2026-115506
Ubuntu:24.04:LTScadaverno fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.04:LTScadaverno fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.10cadaverno fix listedUBUNTU-CVE-2026-115506
Ubuntu:22.04:LTSexpatno fix listedUBUNTU-CVE-2026-115506
Ubuntu:24.04:LTSexpatno fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.04:LTSexpatno fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.10expatno fix listedUBUNTU-CVE-2026-115506
Ubuntu:22.04:LTSinsighttoolkit4no fix listedUBUNTU-CVE-2026-115506
Ubuntu:22.04:LTSmatanzano fix listedUBUNTU-CVE-2026-115506
Ubuntu:24.04:LTSmatanzano fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.04:LTSmatanzano fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.10matanzano fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.10swish-eno fix listedUBUNTU-CVE-2026-115506
Ubuntu:22.04:LTStdomno fix listedUBUNTU-CVE-2026-115506
Ubuntu:24.04:LTStdomno fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.04:LTStdomno fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.10tdomno fix listedUBUNTU-CVE-2026-115506
Ubuntu:22.04:LTSwbxml2no fix listedUBUNTU-CVE-2026-115506
Ubuntu:24.04:LTSwbxml2no fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.04:LTSwbxml2no fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.10wbxml2no fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.04:LTSxmlrpc-cno fix listedUBUNTU-CVE-2026-115506
Ubuntu:26.10xmlrpc-cno fix listedUBUNTU-CVE-2026-115506

Affected products (as reported)

VendorProductVersions
libexpat libexpat 0 – through 2.9.0

Weakness: CWE-776 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References