GHSA-gpv5-7x3g-ghjv — fast-xml-parser
Fix: NaturalIntelligence/fast-xml-parser@9a880b8GHSA-gpv5-7x3g-ghjv is a security vulnerability in fast-xml-parser. A fix is available for fast-xml-parser — see the affected versions and patch details below.
fast-xml-parser regex vulnerability patch could be improved from a safety perspective
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
fast-xml-parsernpmDescription
Summary
This is a comment on https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-6w63-h3fj-q4vw and the patches fixing it.
Details
The code which validates a name calls the validator: https://github.com/NaturalIntelligence/fast-xml-parser/blob/ecf6016f9b48aec1a921e673158be0773d07283e/src/xmlparser/DocTypeReader.js#L145-L153 This checks for the presence of an invalid character. Such an approach is always risky, as it is so easy to forget to include an invalid character in the list. A safer approach is to validate entity names against the XML specification: https://www.w3.org/TR/xml11/#sec-common-syn - an ENTITY name is a Name:
[4] NameStartChar ::= ":" | [A-Z] | "_" | [a-z] | [#xC0-#xD6] | [#xD8-#xF6] | [#xF8-#x2FF] | [#x370-#x37D] |
[#x37F-#x1FFF] | [#x200C-#x200D] | [#x2070-#x218F] | [#x2C00-#x2FEF] | [#x3001-#xD7FF] |
[#xF900-#xFDCF] | [#xFDF0-#xFFFD] | [#x10000-#xEFFFF]
[4a] NameChar ::= NameStartChar | "-" | "." | [0-9] | #xB7 | [#x0300-#x036F] | [#x203F-#x2040]
[5] Name ::= NameStartChar (NameChar)*
so the safest way to validate an entity name is to build a regex to represent this expression and check whether the name given matches the regex. (Something along the lines of /^[name start char class][name char class]*$/.) There's probably a nice way to simplify the explicit list rather than typing it out verbatim using Unicode character properties, but I don't know enough to do so.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | fast-xml-parser | ≥ 4.2.4&&< 4.2.5 | 4.2.5npm install fast-xml-parser@4.2.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fast-xml-parser, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update fast-xml-parser to 4.2.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-gpv5-7x3g-ghjv is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-gpv5-7x3g-ghjv can be triaged on real exposure rather than presence alone.
Tailored to GHSA-gpv5-7x3g-ghjv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-gpv5-7x3g-ghjv in your dependencies?
O3 Security finds GHSA-gpv5-7x3g-ghjv across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.