CVE-2026-27942

Workarounds

Use XML builder with preserveOrder:false or check the input data before passing to builder.

References

Are there any links users can visit to find out more?

Application crashes with stack overflow when user use XML builder with prserveOrder:true for following or similar input

[{
    'foo': [
        { 'bar': [{ '@_V': 'baz' }] }
    ]
}]

Cause: arrToStr was not validating if the input is an array or a string and treating all non-array values as text content.
What kind of vulnerability is it? Who is impacted?

Kodem intelligence

Yes in 5.3.8

1. What is CVE-2026-27942? CVE-2026-27942 is a low-severity security vulnerability in fast-xml-parser (npm), affecting versions >= 5.0.0, < 5.3.8. It is fixed in 5.3.8, 4.5.4.
2. Which versions of fast-xml-parser are affected by CVE-2026-27942? fast-xml-parser (npm) versions >= 5.0.0, < 5.3.8 is affected.
3. Is there a fix for CVE-2026-27942? Yes. CVE-2026-27942 is fixed in 5.3.8, 4.5.4. Upgrade to this version or later.
4. Is CVE-2026-27942 exploitable, and should I be worried? Whether CVE-2026-27942 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-27942 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-27942?
   • Upgrade fast-xml-parser to 5.3.8 or later
   • Upgrade fast-xml-parser to 4.5.4 or later