Memory corruption via overflowing attribute-name counter
Published Jun 21, 2026 · Updated Jun 21, 2026
Integer overflow in getAttributeId in Expat Project libexpat before 2.8.2 allows local users to corrupt memory via malformed XML. The function scans an attribute name for a namespace-prefix colon with a signed int index and increments that index past INT_MAX without a boundary check. Triggering requires a parser to process an attacker-controlled attribute name long enough to reach that boundary; the resulting undefined behavior can expose or alter process memory and interrupt the process.
Summary
What happened
Integer overflow in getAttributeId in Expat Project libexpat before 2.8.2 allows local users to corrupt memory via malformed XML. The function scans an attribute name for a namespace-prefix colon with a signed int index and increments that index past INT_MAX without a boundary check. Triggering requires a parser to process an attacker-controlled attribute name long enough to reach that boundary; the resulting undefined behavior can expose or alter process memory and interrupt the process.
The record
- CVE
- CVE-2026-56405
- Published
- Jun 21, 2026
- Updated
- Jun 21, 2026
- Vendor
- Expat Project
- Product
- libexpat
- Classifications
- CWE-190
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 21, 2026CVE publishedPublication date reported by the CVE source.
- Jun 21, 2026Record updatedLatest update available in the CVE record.
Exploitability
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Is a vulnerable build present?
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- Affected versionversion=0 <2.8.2
What conditions does exploitation require?
What is affected?
Attacks
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Weakness, pattern, technique
Public exploit references
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