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CVE-2026-118370 Details

Description

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.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:8.2 HIGHVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

CNA: [email protected]CVSS-B:5.9 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/libexpat/libexpat	[email protected]	Product
https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L4138-L4140	[email protected]	Product
https://github.com/libexpat/libexpat/commit/1bac53c4fc460a03cd9860f39501c7979f6750ae	[email protected]	Patch
https://github.com/libexpat/libexpat/commit/621cb2c78b253ee023a86bc91d6ddb048481c04c	[email protected]	Patch
https://github.com/libexpat/libexpat/pull/1450	[email protected]	Patch
https://www.vulncheck.com/advisories/libexpat-through-2.9.0-integer-overflow-in-storeatts-via-attindex-and-nprefixes	[email protected]	PatchThird Party Advisory

see all 6 references

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-190	Integer Overflow or Wraparound	[email protected]

Affected Products

Product	Versions
libexpat project libexpat	<= 2.9.0
CPE cpe:2.3:a:libexpat_project:libexpat:::::::: Remediation No remediation found in references.

Change History

3 change records found show changes

Date	Action	Recorded By
Nov 2, 2026	CVE Modified	CISA-ADP
Nov 2, 2026	Initial Analysis	[email protected]
Oct 28, 2026	New CVE Received	[email protected]