Code execution via undersized dictionary allocation
Published Sep 5, 2026 · Updated Sep 8, 2026
Heap-based buffer overflow in XMLSoft libxml2 before 2.15.4 allows local users to execute code through oversized qualified names. The xmlDictAddQString function multiplies an unchecked namelen-plus-plen calculation before allocation, then copies the prefix and name beyond the undersized heap buffer. Exploitation requires attacker-controlled qualified-name data to reach a local consuming process; the overwrite corrupts that process's memory and enables code execution.
Summary
What happened
Heap-based buffer overflow in XMLSoft libxml2 before 2.15.4 allows local users to execute code through oversized qualified names. The xmlDictAddQString function multiplies an unchecked namelen-plus-plen calculation before allocation, then copies the prefix and name beyond the undersized heap buffer. Exploitation requires attacker-controlled qualified-name data to reach a local consuming process; the overwrite corrupts that process's memory and enables code execution.
The record
- CVE
- CVE-2026-86138
- Published
- Sep 5, 2026
- Updated
- Sep 8, 2026
- Vendor
- XMLSoft
- Product
- libxml2
- Classifications
- CWE-190
- 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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Technologies
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