What’s Vulnerable › Vulnerabilities

CVE-2026-83606: xmldom PI grammar regex ReDoS: quadratic backtracking on unterminated processing instructions

• Severity: high (CVSS 8.7 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-01 · updated 2026-09-08
• Weakness: CWE-400

Description

xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. From 0.9.0-beta.9 until 0.9.11, the processing-instruction production in lib/grammar.js lets the greedy S+ separator and lazy Char*? data group repeatedly repartition a long whitespace tail when the required closing ?> is absent. Both parsePI and parseProcessingInstruction apply the expression to the entire remaining source, causing quadratic backtracking during DOMParser.parseFromString() under default options and allowing a small unauthenticated XML input to stall the Node.js event loop. This issue is fixed in @xmldom/xmldom version 0.9.11.

Affected products

• xmldom: from 0.9.0-beta.9, < 0.9.11

References

• https://github.com/xmldom/xmldom/commit/73df6b8bdbd86f904b9e8c3ab9c49aa54ef2802e
• https://github.com/xmldom/xmldom/pull/1039
• https://github.com/xmldom/xmldom/releases/tag/0.9.11
• https://github.com/xmldom/xmldom/security/advisories/GHSA-g53g-w8rj-fmg7
• https://github.com/xmldom/xmldom/security/advisories/GHSA-g53g-w8rj-fmg7

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