Data corruption via negative write-callback lengths
Published Sep 5, 2026 · Updated Sep 8, 2026
Integer coercion in xmlIO in XMLSoft libxml2 before 2.15.4 allows local users to corrupt data through oversized output buffers. xmlOutputWriteCallback passes the size_t result of xmlBufUse to an int-sized write callback without rejecting values at or above INT_MAX, producing a negative length. Reaching the flaw requires a callback-backed output buffer with more than INT_MAX bytes queued; the callback determines whether the result is corruption, disclosure, or a service interruption.
Summary
What happened
Integer coercion in xmlIO in XMLSoft libxml2 before 2.15.4 allows local users to corrupt data through oversized output buffers. xmlOutputWriteCallback passes the size_t result of xmlBufUse to an int-sized write callback without rejecting values at or above INT_MAX, producing a negative length. Reaching the flaw requires a callback-backed output buffer with more than INT_MAX bytes queued; the callback determines whether the result is corruption, disclosure, or a service interruption.
The record
- CVE
- CVE-2026-86143
- Published
- Sep 5, 2026
- Updated
- Sep 8, 2026
- Vendor
- XMLSoft
- Product
- libxml2
- Classifications
- CWE-192
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 5, 2026CVE publishedPublication date reported by the CVE source.
- Sep 8, 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 <2.15.4
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What is affected?
Published CVSS scores
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Attacks
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