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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity High

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
libexpat libexpat unaffected
Version Status Constraints
0 affected ≤ 2.9.0

No data.

No data.

No data.

Project Subscriptions

Vendors Products
Libexpat Project Subscribe
Libexpat Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/libexpat/libexpat cve-icon cve-icon
https://github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b630a8a106a2/expat/lib/xmlparse.c#L3468-L3510 cve-icon cve-icon
https://github.com/libexpat/libexpat/commit/7b0d50e4b1d16fafd55876260701e04279a7489d cve-icon cve-icon
https://github.com/libexpat/libexpat/pull/1444 cve-icon cve-icon
https://www.vulncheck.com/advisories/libexpat-through-2.9.0-null-pointer-dereference-via-external-entity-subparser cve-icon cve-icon
History

Wed, 28 Oct 2026 02:30:00 +0000

Type Values Removed Values Added
Description 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.
Title libexpat through 2.9.0 NULL Pointer Dereference via External Entity Subparser
First Time appeared Libexpat Project
Libexpat Project libexpat
Weaknesses CWE-476
CPEs cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*
Vendors & Products Libexpat Project
Libexpat Project libexpat
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.2, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-28T02:03:18.766Z

Reserved: 2026-10-27T13:04:09.906Z

Link: CVE-2026-117610

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-28T03:17:12.777

Modified: 2026-10-28T03:17:12.777

Link: CVE-2026-117610

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses