Out-of-bounds write in expat - CVE-2026-56132

Vulnerability identifier: #VU144340

CSH Severity: High

CVSS v4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-56132

CWE-ID: CWE-787

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 out-of-bounds write in doProlog when processing scaffolding index data. A remote attacker can supply crafted XML input to cause memory corruption.

expat
LANTIME Operating System Firmware (LTOS)
openEuler
Anolis OS
Fedora
expat-help
expat-devel
expat-debugsource
expat-debuginfo
expat
expat-doc
expat-static
mingw-expat

Install security update from vendor's website.

expat - update to 2.8.2
LANTIME Operating System Firmware (LTOS) - update to 7.10.013
expat-help - addressed in versions 2.2.9-27, 2.4.1-26, 2.5.0-21
expat-devel - addressed in versions 2.2.9-27, 2.4.1-26, 2.5.0-21
expat-debugsource - addressed in versions 2.2.9-27, 2.4.1-26, 2.5.0-21
expat-debuginfo - addressed in versions 2.2.9-27, 2.4.1-26, 2.5.0-21
expat - addressed in versions 2.2.9-27, 2.4.1-26, 2.5.0-21
expat-doc - update to 2.5.0-17
expat-static - update to 2.5.0-17
expat-devel - update to 2.5.0-17
expat - update to 2.5.0-17
mingw-expat - addressed in versions 2.8.2-1.fc43, 2.8.2-1.fc44

• 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