libexpat through 2.10.0 contains an out-of-bounds read vulnerability in unknown_toUtf8() and unknown_toUtf16() in xmltok.c when handling application-registered unknown encodings. Attackers can supply a document ending in a truncated multibyte sequence so the convert callback reads past the parse buffer, leaking adjacent memory or crashing applications.

Attack Vector Network

Attack Complexity High

Privileges Required None

Attack Requirements Present

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact Low

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 Low

Integrity Impact None

Availability Impact Low

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 ≤ 2.10.0

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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
https://github.com/libexpat/libexpat/blob/a70841d9ffa64ddde29ab824ed6305035ebe4c47/expat/lib/xmltok.c#L1274-L1322 cve-icon
https://github.com/libexpat/libexpat/pull/1492 cve-icon
https://www.vulncheck.com/advisories/libexpat-through-2.10.0-out-of-bounds-read-via-unknown-toutf8-and-unknown-toutf16 cve-icon
History

Sat, 07 Nov 2026 14:30:00 +0000

Type Values Removed Values Added
Description libexpat through 2.10.0 contains an out-of-bounds read vulnerability in unknown_toUtf8() and unknown_toUtf16() in xmltok.c when handling application-registered unknown encodings. Attackers can supply a document ending in a truncated multibyte sequence so the convert callback reads past the parse buffer, leaking adjacent memory or crashing applications.
Title libexpat through 2.10.0 Out-of-Bounds Read via unknown_toUtf8 and unknown_toUtf16
First Time appeared Libexpat Project
Libexpat Project libexpat
Weaknesses CWE-126
CPEs cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*
Vendors & Products Libexpat Project
Libexpat Project libexpat
References
Metrics cvssV3_1

{'score': 4.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L'}

cvssV4_0

{'score': 6.3, 'vector': 'CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-11-07T14:17:57.180Z

Reserved: 2026-11-07T12:27:50.865Z

Link: CVE-2026-124317

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses