What is CVE-2026-117610?

CVE-2026-117610 is a medium-severity vulnerability in Libexpat, classified under NULL Pointer Dereference. CVSS score: 5.9/10. Published 2026-10-28.

How severe is CVE-2026-117610?

Medium severity. CVSS v3 base score is 5.9 out of 10.

NULL pointer dereference in Libexpat

CVE-2026-117610

libexpat through 2.9.0 contains a NULL pointer dereference vulnerability in externalEntityInitProcessor2() in lib/xmlparse.c that mishandles the XML_TOK_NONE token from empty input. Attackers who control stream chunking can force an empty non-final first parse on an external entity subparser, causing a later parse to crash the application.

Published 2026-10-28 · last modified 2026-10-28.

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

EPSS: 0.004 (36.7th percentile), scored 2026-10-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 36.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

The 30-day trend appears once there are two daily scores.

Affected products

Libexpat

Weakness classification (CWE)

CWE-476 — NULL Pointer Dereference

References

github.com/libexpat/libexpat/pull/1444 (issue-tracking, patch)
github.com/libexpat/libexpat/commit/7b0d50e4b1d16fafd55876260701e04279a7489d (patch)
github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expa… (technical-description)
github.com/libexpat/libexpat (product)
www.vulncheck.com/advisories/libexpat-through-2.9.0-null-pointer-dereference-vi… (third-party-advisory)

Frequently asked questions

What is CVE-2026-117610?: CVE-2026-117610 is a medium-severity vulnerability in Libexpat, classified under NULL Pointer Dereference. CVSS score: 5.9/10. Published 2026-10-28.
How severe is CVE-2026-117610?: Medium severity. CVSS v3 base score is 5.9 out of 10.