CVE-2026-56405
Received Received - Intake
Integer Overflow in Expat XML Parser

Publication date: 2026-06-21

Last updated on: 2026-06-21

Assigner: MITRE

Description
libexpat before 2.8.2 has an integer overflow in getAttributeId.
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Meta Information
Published
2026-06-21
Last Modified
2026-06-21
Generated
2026-06-21
AI Q&A
2026-06-21
EPSS Evaluated
N/A
NVD
CVE-2026-56405
EUVD
EUVD-2026-38182
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
libexpat libexpat to 2.8.2 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-190 The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.
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Executive Summary

This vulnerability is an integer overflow in the getAttributeId function of the libexpat XML parser library before version 2.8.2.

Specifically, when scanning an attribute name for a prefix colon, the loop counter variable 'i' can exceed the maximum value for an integer (INT_MAX) due to post-increment behavior, which leads to undefined behavior.

This issue was fixed by adding a safeguard to prevent the loop counter from reaching INT_MAX, ensuring the loop terminates safely.

Impact Analysis

The integer overflow in the getAttributeId function can lead to undefined behavior during XML attribute parsing.

According to the CVSS score of 6.9, this vulnerability has a high impact on confidentiality and integrity, and a low impact on availability.

An attacker with local access could potentially exploit this to cause memory corruption or unexpected behavior, which might lead to information disclosure or modification.

Mitigation Strategies

To mitigate this vulnerability, you should update libexpat to version 2.8.2 or later, where the integer overflow issue in the getAttributeId function has been fixed.

The fix prevents the loop counter from exceeding INT_MAX, avoiding undefined behavior that could be exploited.

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