Integer overflow in Libexpat
CVE-2026-102633
libexpat versions 2.7.2 through 2.8.5 contain an integer overflow vulnerability in expat_realloc() function on 32-bit platforms when computing allocation sizes. Attackers supplying malicious XML to applications parsing with vulnerable libexpat can cause heap buffer overflow, memory corruption, or denial of service.
Vulnerability class: Integer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
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/pull/1392 (issue-tracking, patch)
- github.com/libexpat/libexpat/commit/209801d7fbaf07ab74bae8cb32dd2ab9e5846118 (patch)
- github.com/libexpat/libexpat/blob/R_2_8_5/expat/lib/xmlparse.c (technical-description)
- github.com/libexpat/libexpat (product)
- www.vulncheck.com/advisories/libexpat-2.7.2-through-2.8.5-integer-overflow-in-e… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-102633?
- CVE-2026-102633 is a medium-severity vulnerability in Libexpat, classified under Integer Overflow or Wraparound. CVSS score: 5.9/10. Published 2026-09-29.
- How severe is CVE-2026-102633?
- Medium severity. CVSS v3 base score is 5.9 out of 10.