Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-08-20T04:28:04 libexpat: libexpat: Memory corruption vulnerability allows arbitrary code execution or denial of service 4.9 CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L CWE-825

libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks. Thus, a use-after-free can occur. NOTE: this is similar to CVE-2026-50219, CVE-2026-56131 and CVE-2026-56412.

A flaw was found in libexpat. The library's handling of custom encoding callbacks lacks proper tracking of handler call depth, which can lead to a use-after-free vulnerability. This memory corruption flaw could allow a local attacker to cause a denial of service or potentially execute arbitrary code.

Red Hat ships libexpat (packaged as "expat") across many products. All versions of expat prior to 2.8.4 are affected by this use-after-free vulnerability. Exploitation requires triggering the vulnerable code path through custom encoding callbacks, which is not a common usage pattern. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Red Hat Hardened Images 2026-08-27T00:00:00Z RHSA-2026:60451 expat-main-2.8.3-0.1.1.hum1 Red Hat Hardened Images 2026-09-08T00:00:00Z RHSA-2026:65568 expat-main-2.8.4-0.1.hum1 Red Hat Enterprise Linux 10 Fix deferred expat Red Hat Enterprise Linux 10 Fix deferred firefox Red Hat Enterprise Linux 10 Fix deferred thunderbird Red Hat Enterprise Linux 6 Fix deferred compat-expat1 Red Hat Enterprise Linux 6 Fix deferred expat Red Hat Enterprise Linux 7 Fix deferred expat Red Hat Enterprise Linux 7 Fix deferred firefox Red Hat Enterprise Linux 8 Fix deferred expat Red Hat Enterprise Linux 8 Fix deferred firefox Red Hat Enterprise Linux 8 Fix deferred mingw-expat Red Hat Enterprise Linux 8 Fix deferred thunderbird Red Hat Enterprise Linux 8 Fix deferred xmlrpc-c Red Hat Enterprise Linux 9 Fix deferred expat Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Fix deferred openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-76957 https://nvd.nist.gov/vuln/detail/CVE-2026-76957 https://github.com/libexpat/libexpat/pull/1322 https://github.com/libexpat/libexpat/pull/1329