Integer overflow in expat - CVE-2026-56408

Vulnerability identifier: #VU144346

CSH Severity: Medium

CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-56408

CWE-ID: CWE-190

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to cause memory corruption.

The vulnerability exists due to an integer overflow in copyString when copying string data. A remote attacker can supply crafted XML input to cause memory corruption.

expat
Debian Linux
Ubuntu
openEuler
LANTIME Operating System Firmware (LTOS)
expat (Ubuntu package)
expat-help
expat-devel
expat-debugsource
expat-debuginfo
expat
expat (Debian package)

Install security update from vendor's website.

expat - update to 2.8.2
LANTIME Operating System Firmware (LTOS) - update to 7.10.013
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-help - addressed in versions 2.2.9-28, 2.4.1-27, 2.5.0-22, 2.5.0-23
expat-devel - addressed in versions 2.2.9-28, 2.4.1-27, 2.5.0-22, 2.5.0-23
expat-debugsource - addressed in versions 2.2.9-28, 2.4.1-27, 2.5.0-22, 2.5.0-23
expat-debuginfo - addressed in versions 2.2.9-28, 2.4.1-27, 2.5.0-22, 2.5.0-23
expat - addressed in versions 2.2.9-28, 2.4.1-27, 2.5.0-22, 2.5.0-23
expat (Debian package) - update to 2.8.2-1~deb13u1

• https://seclists.org/oss-sec/2026/q2/1030
• https://github.com/libexpat/libexpat/commit/16e2efd867ea8567ffa012210b52ef5918e20817

• Multiple vulnerabilities in libexpat
• Multiple vulnerabilities in Meinberg LANTIME firmware
• openEuler 24.03 LTS SP3 update for expat
• openEuler 24.03 LTS SP1 update for expat
• openEuler 22.03 LTS SP4 update for expat
• openEuler 20.03 LTS SP4 update for expat
• Debian update for expat
• Ubuntu update for expat