How severe is GHSA-x3cc-x39p-42qx?

GHSA-x3cc-x39p-42qx has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-x3cc-x39p-42qx?

GHSA-x3cc-x39p-42qx affects the following packages: fast-xml-parser (npm). Ecosystems affected: npm.

How do I fix GHSA-x3cc-x39p-42qx?

Update fast-xml-parser to 4.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x3cc-x39p-42qx is resolved across your whole dependency graph.

How do I detect GHSA-x3cc-x39p-42qx in my npm dependencies?

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.

How do I mitigate GHSA-x3cc-x39p-42qx if there is no patch (or I can't update yet)?

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.

Is GHSA-x3cc-x39p-42qx actively exploited in the wild?

No public exploit code has been indexed for GHSA-x3cc-x39p-42qx yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-x3cc-x39p-42qx?

GHSA-x3cc-x39p-42qx has an EPSS (Exploit Prediction Scoring System) score of 9.5%, placing it in the 95th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-x3cc-x39p-42qx?

GHSA-x3cc-x39p-42qx is classified as CWE-610 (CWE-610). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-x3cc-x39p-42qx published, and has it been updated?

GHSA-x3cc-x39p-42qx was published on June 13, 2023 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

fast-xml-parser vulnerable to Prototype Pollution through tag or attribute nameGHSA-x3cc-x39p-42qx

MEDIUMFix: NaturalIntelligence/fast-xml-parser@2b032a4

GHSA-x3cc-x39p-42qx is a medium-severity (CVSS 6.5) CWE-610 vulnerability in fast-xml-parser. A fix is available for fast-xml-parser — see the affected versions and patch details below.

Also known asCVE-2021-26920 CVE-2023-26920 GHSA-793h-6f7r-6qvm

Published

Jun 13, 2023

Updated

Jul 8, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

9.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs95th percentile — riskier than 95% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

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.

6Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

fast-xml-parsernpm

113.6Mdownloads / week

Description

In the Druid ingestion system, the InputSource is used for reading data from a certain data source. However, the HTTP InputSource allows authenticated users to read data from other sources than intended, such as the local file system, with the privileges of the Druid server process. This is not an elevation of privilege when users access Druid directly, since Druid also provides the Local InputSource, which allows the same level of access. But it is problematic when users interact with Druid indirectly through an application that allows users to specify the HTTP InputSource, but not the Local InputSource. In this case, users could bypass the application-level restriction by passing a file URL to the HTTP InputSource.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`fast-xml-parser`	all versions	4.1.2`npm install fast-xml-parser@4.1.2`

Affected Products

1 product · 1 configurations

Application

druidapache

< 0.22.0

range

Detection & mitigation playbook

Open-source dependency

Detect
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 4.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-x3cc-x39p-42qx 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.

Frequently Asked Questions

### Impact As a part of this vulnerability, user was able to se code using `__proto__` as a tag or attribute name. ```js const { XMLParser, XMLBuilder, XMLValidator} = require("fast-xml-parser"); let XMLdata = "<__proto__><polluted>hacked</polluted></__proto__>" const parser = new XMLParser(); let jObj = parser.parse(XMLdata); console.log(jObj.polluted) // should return hacked ``` ### Patches The problem has been patched in v4.1.2 ### Workarounds User can check for "__proto__" in the XML string before parsing it to the parser. ### References https://gist.github.com/Sudistark/a5a45bd080