Out-of-bounds read via negative entity textLen
Published Jun 21, 2026 · Updated Jun 21, 2026
Integer overflow in libexpat before 2.8.2 allows local users to read beyond an entity buffer by parsing crafted XML. storeEntityValue casts a pool length above INT_MAX to int, making textLen negative; doProlog then computes textEnd before textPtr and walks beyond the buffer. Exploitation requires an internal entity value exceeding INT_MAX and local parsing of attacker-controlled XML, exposing process memory and corrupting parser state.
Summary
What happened
Integer overflow in libexpat before 2.8.2 allows local users to read beyond an entity buffer by parsing crafted XML. storeEntityValue casts a pool length above INT_MAX to int, making textLen negative; doProlog then computes textEnd before textPtr and walks beyond the buffer. Exploitation requires an internal entity value exceeding INT_MAX and local parsing of attacker-controlled XML, exposing process memory and corrupting parser state.
The record
- CVE
- CVE-2026-56407
- 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
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What is affected?
Published CVSS scores
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Attacks
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