Protection mechanism failure in expat - CVE-2026-56412

Vulnerability identifier: #VU144350

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-2026-56412

CWE-ID: CWE-693

Exploitation vector: Remote access

Exploit availability: Public exploit is available

The vulnerability allows a remote attacker to cause memory corruption.

The vulnerability exists due to missing control flow integrity checks in doCdataSection when handling XML_TOK_DATA_CHARS callbacks. A remote attacker can trigger unsafe handler calls to cause memory corruption.

This issue is described as a hole in the fix for CVE-2026-50219.

expat
Debian Linux
Ubuntu
openEuler
Anolis OS
Fedora
LANTIME Operating System Firmware (LTOS)
expat (Ubuntu package)
expat-debugsource
expat-help
expat-devel
expat-debuginfo
expat
expat-doc
expat-static
mingw-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-debugsource - addressed in versions 2.2.9-28, 2.2.9-33, 2.4.1-27, 2.4.1-31, 2.5.0-22, 2.5.0-23, 2.5.0-27, 2.8.1-8
expat-help - addressed in versions 2.2.9-28, 2.2.9-33, 2.4.1-27, 2.4.1-31, 2.5.0-22, 2.5.0-23, 2.5.0-27, 2.8.1-8
expat-devel - addressed in versions 2.2.9-28, 2.2.9-33, 2.4.1-27, 2.4.1-31, 2.5.0-22, 2.5.0-23, 2.5.0-27, 2.8.1-8
expat-debuginfo - addressed in versions 2.2.9-28, 2.2.9-33, 2.4.1-27, 2.4.1-31, 2.5.0-22, 2.5.0-23, 2.5.0-27, 2.8.1-8
expat - addressed in versions 2.2.9-28, 2.2.9-33, 2.4.1-27, 2.4.1-31, 2.5.0-22, 2.5.0-23, 2.5.0-27, 2.8.1-8
expat-devel - update to 2.5.0-16
expat-doc - update to 2.5.0-16
expat-static - update to 2.5.0-16
expat - update to 2.5.0-16
mingw-expat - addressed in versions 2.8.2-1.fc43, 2.8.2-1.fc44
expat (Debian package) - update to 2.8.2-1~deb13u1

• Exploit #12939 - PoC-Exploit (Exploits for the CVEs) (August 21, 2026)

• https://seclists.org/oss-sec/2026/q2/1030
• https://github.com/libexpat/libexpat/blob/R_2_8_2/expat/Changes

• Multiple vulnerabilities in libexpat
• Multiple vulnerabilities in Meinberg LANTIME firmware
• Fedora 44 update for mingw-expat
• Fedora 43 update for mingw-expat
• 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
• Anolis OS update for expat
• Debian update for expat
• 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
• openEuler 24.03 LTS SP4 update for expat
• Ubuntu update for expat