fast-xml-parser has stack overflow in XMLBuilder with preserveOrder
Impact
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?
Patches
Yes in 5.3.8
Workarounds
Use XML builder with preserveOrder:false or check the input data before passing to builder.
References
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | fast-xml-parser | >= 5.0.0, < 5.3.8, >= 4.0.0-beta.0, < 4.5.4 | 5.3.8, 4.5.4 |
References
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-fj3w-jwp8-x2g3
- https://nvd.nist.gov/vuln/detail/CVE-2026-27942
- https://github.com/NaturalIntelligence/fast-xml-parser/pull/791
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/c13a961910f14986295dd28484eee830fa1a0e8a
- https://github.com/NaturalIntelligence/fast-xml-parser
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U- Weakness (CWE)
CWE-120- Platform
- npm
- Package
fast-xml-parser- Disclosed
- 26.02.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-fj3w-jwp8-x2g3 - CC BY 4.0
Vulnerability history: fast-xml-parser
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 12
- First → latest
- 08.2021 07.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 6
- Medium 3
- Low 2
Disclosures per year
- 2021: 1
- 2022: 0
- 2023: 2
- 2024: 1
- 2025: 0
- 2026: 8
-
fast-xml-parser has stack overflow in XMLBuilder with preserveOrder this entry
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