Application hang via UTF-16 surrogate misclassification
Published Aug 10, 2026 · Updated Aug 10, 2026
Out-of-bounds read in libexpat before 2.8.3 allows remote attackers to hang applications that parse crafted XML over a network. The *_toUtf16 conversion macros test only the upper five bits of the final code unit, so a low surrogate is mistaken for a high surrogate and the input pointer stops advancing. Exposure requires a build with 16-bit character support, such as Firefox or Windows builds; the resulting infinite loop interrupts the parsing application.
Summary
What happened
Out-of-bounds read in libexpat before 2.8.3 allows remote attackers to hang applications that parse crafted XML over a network. The *_toUtf16 conversion macros test only the upper five bits of the final code unit, so a low surrogate is mistaken for a high surrogate and the input pointer stops advancing. Exposure requires a build with 16-bit character support, such as Firefox or Windows builds; the resulting infinite loop interrupts the parsing application.
The record
- CVE
- CVE-2026-72522
- Published
- Aug 10, 2026
- Updated
- Aug 10, 2026
- Vendor
- Expat Project
- Product
- libexpat
- Classifications
- CWE-125, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 10, 2026CVE publishedPublication date reported by the CVE source.
- Aug 10, 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 <2.8.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
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Technologies
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Your stack
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