Answer in brief
CVE-2026-126066 records a Low severity (CVSS 3.7) vulnerability in fast-xml-parser: Quadratic CPU consumption scanning unterminated stop-node tags. The current sources do not mark it as known exploited. The current feed maps NaturalIntelligence/fast-xml-parser (generic), fast-xml-parser (npm). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 3.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps NaturalIntelligence/fast-xml-parser (generic), fast-xml-parser (npm). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| NaturalIntelligence/fast-xml-parsergeneric | <5.12.0 | 5.12.0 |
| fast-xml-parsernpm | <=5.11.2 | 5.12.0 |
Published upstream
Nov 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Nov 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Nov 10, 2026
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Prior to 5.12.0, when the non-default stopNodes option is enabled, readStopNodeData() in OrderedObjParser.js calls readTagExp() for each less-than character in an unterminated stop-node body and repeatedly rescans the remaining input while looking for a closing greater-than character. An attacker who supplies XML containing many tag fragments without a later closing character can cause quadratic rescanning before parsing fails, blocking a Node.js event loop and causing CPU-exhaustion denial of service. This issue is fixed in version 5.12.0.
Quoted source text, attributed separately from HOL analysis.