Service stall via unterminated processing-instruction backtracking
Published Sep 1, 2026 · Updated Sep 1, 2026
Regular expression denial of service in xmldom 0.9.0-beta.9 through 0.9.10 allows remote attackers to stall the Node.js event loop. The processing-instruction regex in lib/grammar.js lets its greedy whitespace separator and lazy data group repeatedly repartition a trailing whitespace run when the required closing sequence is absent. Parsing one crafted XML document with DOMParser.parseFromString under default options consumes quadratic CPU time, blocking the application event loop without exposing or modifying data.
Summary
What happened
Regular expression denial of service in xmldom 0.9.0-beta.9 through 0.9.10 allows remote attackers to stall the Node.js event loop. The processing-instruction regex in lib/grammar.js lets its greedy whitespace separator and lazy data group repeatedly repartition a trailing whitespace run when the required closing sequence is absent. Parsing one crafted XML document with DOMParser.parseFromString under default options consumes quadratic CPU time, blocking the application event loop without exposing or modifying data.
The record
- CVE
- CVE-2026-83606
- Published
- Sep 1, 2026
- Updated
- Sep 1, 2026
- Vendor
- xmldom
- Product
- xmldom
- Classifications
- CWE-400, CWE-1333, T1499.004
- 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=>= 0.9.0-beta.9, < 0.9.11
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 unterminated processing-instruction proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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