GHSA-FJ3W-JWP8-X2G3

Vulnerability from github – Published: 2026-02-26 22:33 – Updated: 2026-03-06 22:00
VLAI
Summary
fast-xml-parser has stack overflow in XMLBuilder with preserveOrder
Details

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

Are there any links users can visit to find out more?

Severity
2.7 (Low)
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
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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "fast-xml-parser"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.0.0"
            },
            {
              "fixed": "5.3.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "fast-xml-parser"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0-beta.0"
            },
            {
              "fixed": "4.5.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27942"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-120"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-26T22:33:10Z",
    "nvd_published_at": "2026-02-26T02:16:22Z",
    "severity": "LOW"
  },
  "details": "### Impact\nApplication crashes with stack overflow when user use XML builder with `prserveOrder:true` for following or similar input \n\n```\n[{\n    \u0027foo\u0027: [\n        { \u0027bar\u0027: [{ \u0027@_V\u0027: \u0027baz\u0027 }] }\n    ]\n}]\n```\n\nCause: `arrToStr` was not validating if the input is an array or a string and treating all non-array values as text content.\n_What kind of vulnerability is it? Who is impacted?_\n\n### Patches\nYes in 5.3.8\n\n### Workarounds\nUse XML builder with `preserveOrder:false` or check the input data before passing to builder.\n\n### References\n[_Are there any links users can visit to find out more?_](https://github.com/NaturalIntelligence/fast-xml-parser/pull/791)",
  "id": "GHSA-fj3w-jwp8-x2g3",
  "modified": "2026-03-06T22:00:11Z",
  "published": "2026-02-26T22:33:10Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-fj3w-jwp8-x2g3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27942"
    },
    {
      "type": "WEB",
      "url": "https://github.com/NaturalIntelligence/fast-xml-parser/pull/791"
    },
    {
      "type": "WEB",
      "url": "https://github.com/NaturalIntelligence/fast-xml-parser/commit/c13a961910f14986295dd28484eee830fa1a0e8a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/NaturalIntelligence/fast-xml-parser"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "fast-xml-parser has stack overflow in XMLBuilder with preserveOrder"
}


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