CVE-2026-56404
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 addBinding.
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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-2026-56404
EUVD
EUVD-2026-38181
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 a signed integer overflow in the addBinding function of the libexpat library before version 2.8.2. It happens when calculating the length of a URI string, where the loop counter can exceed the maximum value of a signed integer due to post-increment operations. Although the URI length is limited by the pool block size, this overflow causes undefined behavior at the boundary.

Impact Analysis

The integer overflow in addBinding can lead to undefined behavior, which may cause memory corruption or other unexpected program behavior. According to the CVSS score of 6.9, this vulnerability has a high impact on confidentiality and integrity, and a low impact on availability. Exploiting this flaw could allow an attacker with local access to compromise the affected system's data integrity and confidentiality.

Mitigation Strategies

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

The fix addresses the signed integer overflow by properly handling the integer arithmetic in the URI length calculation.

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