Process hang via zero-advance DTD token loop
Published Mar 16, 2026 · Updated Mar 16, 2026
Infinite loop in Expat Project libexpat before 2.7.5 allows local users to hang an XML-parsing process via crafted DTD content. In entityValueProcessor, XmlPrologTok can repeatedly return XML_TOK_INSTANCE_START without advancing the input pointer. Exposure requires an application to use both XML_ExternalEntityParserCreate and XML_SetParamEntityParsing; a triggering document consumes a parser thread until the process is terminated.
Summary
What happened
Infinite loop in Expat Project libexpat before 2.7.5 allows local users to hang an XML-parsing process via crafted DTD content. In entityValueProcessor, XmlPrologTok can repeatedly return XML_TOK_INSTANCE_START without advancing the input pointer. Exposure requires an application to use both XML_ExternalEntityParserCreate and XML_SetParamEntityParsing; a triggering document consumes a parser thread until the process is terminated.
The record
- CVE
- CVE-2026-32777
- Published
- Mar 16, 2026
- Updated
- Mar 16, 2026
- Vendor
- Expat Project
- Product
- libexpat
- Classifications
- CWE-835, T1499.004
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 16, 2026CVE publishedPublication date reported by the CVE source.
- Mar 16, 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 <2.7.5
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- OSS-Fuzz testcase 5419974373212160proof of concept · demonstrated
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Technologies
Your stack
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Your stack
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