Local code execution via SYSTEM identifier overflow
Published Jun 21, 2026 · Updated Jun 21, 2026
Integer overflow in xmlwf in Expat Project libexpat before 2.8.2 allows local users to trigger a heap buffer overflow. resolveSystemId adds the base-path and external-entity SYSTEM identifier lengths, multiplies the sum by the wide-character size without overflow checks, and then copies both strings into the undersized allocation. Exploitation requires a Windows wide-character build of xmlwf to process a crafted external entity; resulting heap corruption exposes process data or enables code execution in xmlwf's security context.
Summary
What happened
Integer overflow in xmlwf in Expat Project libexpat before 2.8.2 allows local users to trigger a heap buffer overflow. resolveSystemId adds the base-path and external-entity SYSTEM identifier lengths, multiplies the sum by the wide-character size without overflow checks, and then copies both strings into the undersized allocation. Exploitation requires a Windows wide-character build of xmlwf to process a crafted external entity; resulting heap corruption exposes process data or enables code execution in xmlwf's security context.
The record
- CVE
- CVE-2026-56410
- Published
- Jun 21, 2026
- Updated
- Jun 21, 2026
- Vendor
- Expat Project
- Product
- libexpat
- Classifications
- CWE-190, T1203
- 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
Present is not the same as exploitable
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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?
Published CVSS scores
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Attacks
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Weakness, pattern, technique
Public exploit references
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Technologies
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Your stack
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