Vulnerability in Libexpat
CVE-2026-124317
libexpat through 2.10.0 contains an out-of-bounds read vulnerability in unknown_toUtf8() and unknown_toUtf16() in xmltok.c when handling application-registered unknown encodings. Attackers can supply a document ending in a truncated multibyte sequence so the convert callback reads past the parse buffer, leaking adjacent memory or crashing applications.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/libexpat/libexpat (product)
- github.com/libexpat/libexpat/blob/a70841d9ffa64ddde29ab824ed6305035ebe4c47/expa… (technical-description)
- github.com/libexpat/libexpat/pull/1492 (issue-tracking, patch)
- www.vulncheck.com/advisories/libexpat-through-2.10.0-out-of-bounds-read-via-unk… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-124317?
- CVE-2026-124317 is a medium-severity vulnerability in Libexpat, classified under Buffer Over-read. CVSS score: 4.8/10. Published 2026-11-07.
- How severe is CVE-2026-124317?
- Medium severity. CVSS v3 base score is 4.8 out of 10.