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xmldom: End-tag Whitespace-Trim Regex ReDoS — quadratic backtracking in the 0.8.x end-tag parser

Node.js · CVE-2026-83619
0 news outlets0 CERTs and agencies0 researchers

What is it?

xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. From 0.7.0 until 0.8.15, the release-0.8.x parser in lib/sax.js trims captured end-tag names with the unanchored global expression /[ \t\n\r]+$/g. For an end tag containing a long whitespace run followed by a non-whitespace character, the expression retries from each possible starting position and backtracks quadratically before failing its end anchor. DOMParser.parseFromString() reaches the path under default options, allowing a small unauthenticated XML input to stall the Node.js event loop; the 0.9.x and unscoped npm lines do not contain this expression. This issue is fixed in @xmldom/xmldom version 0.8.15.

Evidence

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Exploitation

  • Public proof of concept
  • Exploited in the wild
  • Listed as known exploited
CVSS
8.7
EPSS
0.5%
First seen
6 d ago
Status
corroborated

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