Medium [CVE-2026-76957] Memory corruption vulnerability allows arbitrary code execution or denial of service
This medium-severity Red Hat Linux advisory covers CVE-2026-76957 affecting Red Hat Hardened Images, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6.
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Summary
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.
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.
Red Hat severity: Moderate — CVSS 4.9 (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L). Weakness: CWE-825.
Affected Red Hat products: Red Hat Hardened Images; Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat OpenShift Container Platform 4. Red Hat fixing advisory: RHSA-2026:60451, RHSA-2026:65568.
Affected products named by the advisory: Red Hat package: expat; Red Hat package: firefox; Red Hat package: thunderbird; Red Hat package: compat-expat1; and 2 more.
Affected products named by the advisory: Red Hat package: mingw-expat; Red Hat package: xmlrpc-c.
- < 2.8.4
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
- expat-main-2.8.3-0.1.1.hum1
- expat-main-2.8.4-0.1.hum1
- RHSA-2026:60451
- RHSA-2026:65568
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 8 days ago·verify at source
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