Validation bypass via malformed XML end tags
Published Sep 1, 2026 · Updated Sep 1, 2026
Input validation bypass in affected xmldom releases allows attackers to pass malformed XML through parse-before-trust checks. DOMParser.parseFromString() accepts an end tag whose valid name precedes a line break and residue because lib/sax.js uses a multiline-anchored validator, then closes the element and silently discards the residue. The application must parse attacker-controlled XML and equate error-free parsing with well-formedness; the result is validation bypass and document misinterpretation, not content injection.
Summary
What happened
Input validation bypass in affected xmldom releases allows attackers to pass malformed XML through parse-before-trust checks. DOMParser.parseFromString() accepts an end tag whose valid name precedes a line break and residue because lib/sax.js uses a multiline-anchored validator, then closes the element and silently discards the residue. The application must parse attacker-controlled XML and equate error-free parsing with well-formedness; the result is validation bypass and document misinterpretation, not content injection.
The record
- CVE
- CVE-2026-83611
- Published
- Sep 1, 2026
- Updated
- Sep 1, 2026
- Vendor
- xmldom
- Product
- xmldom
- Classifications
- CWE-1286
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 1, 2026CVE publishedPublication date reported by the CVE source.
- Sep 1, 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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=<= 0.6.0
- Affected versionversion=>= 0.7.0, < 0.8.15
- Affected versionversion=>= 0.9.0, < 0.9.12
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
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
- Upstream malformed end-tag proof of conceptproof of concept · demonstrated
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Technologies
Your stack
See the directory against your own environment.
Your stack
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