# CVE-2026-83606

## Summary

- **CVE ID:** CVE-2026-83606
- **Severity:** HIGH
- **CVSS Score:** 8.7 (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)
- **CWE:** CWE-400, CWE-1333
- **Published:** Sep 1, 2026
- **Last Modified:** Sep 1, 2026

## 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 — xmldom (>= 0.9.0-beta.9, < 0.9.11)
- @xmldom — xmldom (>= 0.9.0-beta.9, < 0.9.11)

## References

- [CNA](https://github.com/xmldom/xmldom/security/advisories/GHSA-g53g-w8rj-fmg7)
- [CNA](https://github.com/xmldom/xmldom/pull/1039)
- [CNA](https://github.com/xmldom/xmldom/commit/73df6b8bdbd86f904b9e8c3ab9c49aa54ef2802e)
- [CNA](https://github.com/xmldom/xmldom/releases/tag/0.9.11)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.30%
- **EPSS Percentile:** 22.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._