What is CVE-2026-76957?

CVE-2026-76957 is a medium-severity vulnerability in Libexpat Project, classified under Use After Free. CVSS score: 4.9/10. Published 2026-08-20.

How severe is CVE-2026-76957?

Medium severity. CVSS v3 base score is 4.9 out of 10.

Use After Free in Libexpat Project

CVE-2026-76957

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.

Vulnerability class: Use-After-Free

Published 2026-08-20 · last modified 2026-09-08.

CVSS v3 metric

CVSS v3 base score 4.9 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.001 (1.0th percentile), scored 2026-10-06.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 1st percentile — 1.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.001 · newest: 0.001 · change: -0.000

Affected products

Weakness classification (CWE)

CWE-416 — Use After Free

References

github.com/libexpat/libexpat/pull/1322 (Patch, Issue Tracking, Vendor Advisory)
github.com/libexpat/libexpat/pull/1329 (Patch, Issue Tracking)

Frequently asked questions

What is CVE-2026-76957?: CVE-2026-76957 is a medium-severity vulnerability in Libexpat Project, classified under Use After Free. CVSS score: 4.9/10. Published 2026-08-20.
How severe is CVE-2026-76957?: Medium severity. CVSS v3 base score is 4.9 out of 10.