What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-05-07 · updated 2026-10-26
• Weakness: CWE-91

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.

Affected products

• NaturalIntelligence fast-xml-parser: before 5.7.0 — fixed in 5.7.0

How to fix

Upgrade to a fixed version: NaturalIntelligence fast-xml-parser 5.7.0. Check the vendor advisory for mitigations.

References

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

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