Medium 5.9Published Oct 27, 2026

CVE-2026-118370libexpat through 2.9.0 Integer Overflow in storeAtts via attIndex and nPrefixes

Updated under an hour ago (Oct 29, 2026, 5:00 AM ET)

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Every CVE for libexpat

Exploited in the last 30 days

libexpat through 2.9.0 contains a signed integer overflow vulnerability in storeAtts() in lib/xmlparse.c that allows attackers to trigger out-of-bounds writes via oversized attribute counts. Attackers can supply a multi-gigabyte document with a start tag carrying over 2^30 attributes to overflow attIndex and nPrefixes, crashing applications or corrupting heap memory.

CVSS: 5.9 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-190
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: VulnCheck
NVD analysis: Awaiting Analysis
Record last updated: Oct 27, 2026
First seen by InfoSec Signals: Oct 27, 2026

Affected products

Affected products

libexpat libexpat libexpat:libexpat (from the name)	through 2.9.0	CNA record

References

References

https://github.com/libexpat/libexpat/pull/1450	patch, issue-tracking
https://github.com/libexpat/libexpat/commit/1bac53c4fc460a03cd9860f39501c7979f6750ae	patch
https://github.com/libexpat/libexpat/commit/621cb2c78b253ee023a86bc91d6ddb048481c04c	patch
https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L4138-L4140	technical-description
https://github.com/libexpat/libexpat	product
https://www.vulncheck.com/advisories/libexpat-through-2.9.0-integer-overflow-in-storeatts-via-attindex-and-nprefixes	third-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.