Inefficient algorithmic complexity in expat - CVE-2026-45186

Vulnerability identifier: #VU149949

CSH Severity: Medium

CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-45186

CWE-ID: CWE-407

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to perform a denial of service attack.

The vulnerability exists due to computational complexity of attribute name collision checks. A remote attacker can pass specially crafted XML input to the application and perform a denial of service attack.

expat
Debian Linux
Anolis OS
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Ubuntu
openEuler
Maximo Application Suite - Monitor Component
expat
expat-debuginfo
expat-debugsource
expat-devel
expat-help
expat (Red Hat package)
expat-doc
expat-static
expat (Ubuntu package)
expat (Debian package)

Install updates from vendor's website.

expat - update to 2.8.1
Maximo Application Suite - Monitor Component - addressed in versions 9.0.25, 9.1.15, 9.2.4
expat - addressed in versions 2.2.9-24, 2.4.1-23, 2.5.0-19
expat-debuginfo - addressed in versions 2.2.9-24, 2.4.1-23, 2.5.0-19
expat-debugsource - addressed in versions 2.2.9-24, 2.4.1-23, 2.5.0-19
expat-devel - addressed in versions 2.2.9-24, 2.4.1-23, 2.5.0-19
expat-help - addressed in versions 2.2.9-24, 2.4.1-23, 2.5.0-19
expat - addressed in versions 2.5.0-2, 2.5.0-13
expat-devel - addressed in versions 2.5.0-2, 2.5.0-13
expat (Red Hat package) - update to 2.5.0-2.el8_10
expat-doc - update to 2.5.0-13
expat-static - update to 2.5.0-13
expat (Ubuntu package) - addressed in versions 2.1.0-4ubuntu1.4+esm12, 2.1.0-7ubuntu0.16.04.5+esm13, 2.2.5-3ubuntu0.9+esm4, 2.2.9-1ubuntu0.8+esm2, 2.4.7-1ubuntu0.8, 2.6.1-2ubuntu0.5, 2.7.4-1ubuntu0.1
expat (Debian package) - update to 2.8.2-1~deb13u1

• https://github.com/libexpat/libexpat/pull/1216
• http://www.openwall.com/lists/oss-security/2026/05/11/16
• https://bugzilla.redhat.com/show_bug.cgi?id=2468575
• https://cert-portal.siemens.com/productcert/html/ssa-082556.html
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45186.json

• Denial of service in libexpat
• Debian update for expat
• openEuler 22.03 LTS SP4 update for expat
• openEuler 20.03 LTS SP4 update for expat
• openEuler 24.03 LTS SP3 update for expat
• openEuler 24.03 LTS update for expat
• openEuler 24.03 LTS SP1 update for expat
• Anolis OS update for expat
• Anolis OS update for expat
• Red Hat Enterprise Linux 8 update for expat
• Ubuntu update for expat
• Multiple vulnerabilities in IBM Maximo Application Suite - Monitor Component