Home/CVE/fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based li
CVE

CVE-2026-27942

fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based li

fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. Prior to version 5.3.8, the application crashes with stack overflow when user use XML builder with preserveOrder:true. Version 5.3.8 fixes the issue.

As a workaround, use XML builder with preserveOrder:false or check the input data before passing to builder.

HIGH · CVSS 7.5 EPSS 0.00018
Schedule remediation
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
▤

Affected Products & Versions

2
naturalintelligence fast-xml-parser< 4.5.4
naturalintelligence fast-xml-parser>= 5.0.0 and < 5.3.8
▤

Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
npm fast-xml-parser LOW fixed in 5.3.8
▣

Scoring & Timeline

7.5
HIGH · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD26 Feb 2026 · 02:16 AM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
⚑

Vendor Advisories

5
rhsaRHSA-2026:12277Important
rhsaRHSA-2026:6174Important
rhsaRHSA-2026:6802Important
rhsaRHSA-2026:7128Important
rhsaRHSA-2026:7110Important
🔗

References & Sources

3
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/NaturalIntelligence/fast-xml-parser/commit/c13a961910f14986295dd28484eee830fa1a0e8aPatch
https://github.com/NaturalIntelligence/fast-xml-parser/pull/791Issue TrackingPatch
https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-fj3w-jwp8-x2g3Vendor Advisory
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