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8.3

Expat library can be slowed by crafted XML

CVE-2026-115506 · published 13 days ago
Summary

The Expat XML parsing library (versions up to 2.9.0) can be forced to spend a long time processing specially made XML files that contain many nested entities. This can delay applications that rely on the library, potentially causing service slowdown. Update to a newer version of Expat or apply patches that improve the entity‑expansion check.

What to do
  • Update expat to version 2.10.0-r0.
  • Update expat to version 2.8.3-1~deb13u1.aikido.22.
  • Update rootio-expat to version 2.8.3-1~deb13u1.aikido.22.
  • Update expat to version 2.8.3-1~deb13u1.aikido.23.
  • Update rootio-expat to version 2.8.3-1~deb13u1.aikido.23.
  • Update expat to version 2.9.0-1~deb13u1.aikido.24.
  • Update rootio-expat to version 2.9.0-1~deb13u1.aikido.24.
  • Update expat to version 2.5.0-1+deb12u5.aikido.28.
  • Update rootio-expat to version 2.5.0-1+deb12u5.aikido.28.
Affected software
Ecosystem VendorProductAffected versions
Alpine:v3.21 – expat < 2.10.0-r0
Fix: upgrade to 2.10.0-r0
Debian:12 debian expat All versions
– libexpat libexpat <= 2.9.0
Ubuntu:Pro:14.04:LTS canonical coin3 All versions
Ubuntu:Pro:14.04:LTS canonical expat All versions
Ubuntu:Pro:14.04:LTS canonical vnc4 All versions
Ubuntu:Pro:14.04:LTS canonical vtk All versions
Ubuntu:Pro:14.04:LTS canonical xmlrpc-c All versions
Ubuntu:Pro:16.04:LTS canonical ayttm All versions
Ubuntu:Pro:16.04:LTS canonical cableswig All versions
Ubuntu:16.04:LTS canonical cadaver All versions
Ubuntu:16.04:LTS canonical gdcm All versions
Ubuntu:16.04:LTS canonical insighttoolkit4 All versions
Ubuntu:Pro:16.04:LTS canonical libxmltok All versions
Ubuntu:16.04:LTS canonical matanza All versions
Ubuntu:16.04:LTS canonical smart All versions
Ubuntu:Pro:16.04:LTS canonical swish-e All versions
Ubuntu:16.04:LTS canonical tdom All versions
Ubuntu:16.04:LTS canonical wbxml2 All versions
Root:Debian:13 – expat < 2.8.3-1~deb13u1.aikido.22
< 2.8.3-1~deb13u1.aikido.23
< 2.9.0-1~deb13u1.aikido.24
Fix: upgrade to 2.8.3-1~deb13u1.aikido.22
Root:Debian:13 – rootio-expat < 2.8.3-1~deb13u1.aikido.22
< 2.8.3-1~deb13u1.aikido.23
< 2.9.0-1~deb13u1.aikido.24
Fix: upgrade to 2.8.3-1~deb13u1.aikido.22
Root:Debian:12 – expat < 2.5.0-1+deb12u5.aikido.28
Fix: upgrade to 2.5.0-1+deb12u5.aikido.28
Root:Debian:12 – rootio-expat < 2.5.0-1+deb12u5.aikido.28
Fix: upgrade to 2.5.0-1+deb12u5.aikido.28
– libexpat_project libexpat <= 2.9.0
cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*
Original advisory text
libexpat through 2.9.0 Denial of Service via Billion Laughs Detection Delay
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.
References
Fix within
Internet-facing 14 days
Internal 60 days
  • Not known to be exploited
  • Can be exploited automatically
  • Gives an attacker partial control
Severity
8.3 High
Exploitation
<1% chance of attack within 30 days
Type
CWE-776Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
Timeline
Published22 Oct 2026
Updated4 Nov 2026
First seen22 Oct 2026
Sources
CVE-2026-115506 · NVD
CVE-2026-115506 · OSV
DEBIAN-CVE-2026-115506 · OSV
CVE-2026-115506 · MITRE
UBUNTU-CVE-2026-115506 · OSV
ROOT-OS-DEBIAN-13-CVE-2026-115506 · OSV
ROOT-OS-DEBIAN-12-CVE-2026-115506 · OSV
ALPINE-CVE-2026-115506 · OSV
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