Vulnerabilities in pkg:npm/fast-xml-builder

PACKAGE
Advisory Identifier: GHSA-5wm8-gmm8-39j9
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Advisory Summary

CVE-2026-44665 is a HIGH (CVSS 6.1) fast-xml-builder allows attribute values with vulnerability (CWE-91: XML Injection (aka Blind XPath Injection)) affecting Fast xml builder libraries in the npm ecosystem. The issue involves fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes. Remediation is available by upgrading affected packages to version 1.1.7.

2 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:npm/fast-xml-builder

2 Known Advisory Record(s)

Vulnerability advisories affecting package pkg:npm/fast-xml-builder. Select an advisory below to view technical details or fixes.

Advisory ID CVE / NVD Severity Summary
GHSA-5wm8-gmm8-39j9 CVE-2026-44665 HIGH fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes
GHSA-45c6-75p6-83cc CVE-2026-44664 MODERATE fast-xml-builder Comment Value regex can be bypassed

CVE-2026-44665 at a Glance

CVE Identifier CVE-2026-44665
GHSA Identifier GHSA-5wm8-gmm8-39j9
Severity HIGH
CVSS v3.1 Base Score 6.1
CWE Classification CWE-91: XML Injection (aka Blind XPath Injection)
Affected Product Fast xml builder
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 6.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-44665

To remediate this vulnerability, upgrade all affected Fast xml builder dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

fast-xml-builder fixed: 1.1.7 
npm install fast-xml-builder@1.1.7
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls fast-xml-builder

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-44665, inspect your project dependencies using npm:

npm ls fast-xml-builder

Analyze the terminal output to locate any version of Fast xml builder in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.1.7), your application is affected.

Note: The npm ls fast-xml-builder command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-91: XML Injection (aka Blind XPath Injection), where the product does not properly neutralize special elements that are used in xml, allowing attackers to modify the syntax, content, or commands of the xml before it is processed by an end system. In Fast xml builder, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

# Summary When an input data has quotes in attribute values but process entities is not enabled, it breaks the attribute value into multiple attributes. This gives the room for an attacker to insert unwanted attributes to the XML/HTML. ## Detail Malicious Input ``` { a: { "@_attr": '" onClick="alert(1)' } } ``` Output ```xml <a attr="" onClick="alert(1)"></a> ``` ### Workarounds If you're not ignoring attributes then keep processEntities flag true.

CVE-2026-44665 Affected Fast xml builder Versions

1 component(s)
Fixed Versions:
1.1.7
Product / Package Ecosystem Affected Versions Fixed Version
fast-xml-builder
npm/fast-xml-builder
npm
< 1.1.7
1.1.7

References

GitHub Advisory / Wiki ADVISORY
https://github.com/NaturalIntelligence/fast-xml-builder/security/advisories/GHSA-5wm8-gmm8-39j9
NVD — CVE-2026-44665 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-44665
Fast xml builder Source Repository REPOSITORY
https://github.com/NaturalIntelligence/fast-xml-builder

Frequently Asked Questions

What is CVE-2026-44665?
CVE-2026-44665 is a security vulnerability in Fast xml builder involving fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes under CWE-91: XML Injection (aka Blind XPath Injection).
Which Fast xml builder versions are affected?
Affected versions include releases prior to 1.1.7 across affected packages: fast-xml-builder.
What version fixes CVE-2026-44665?
Upgrading to 1.1.7 (or the latest patched release for your respective branch) resolves the vulnerability.
Is fast-xml-builder affected?
Yes, fast-xml-builder is affected in releases prior to 1.1.7. Upgrade your dependency to 1.1.7 or later.
What is the CVSS score of CVE-2026-44665?
CVE-2026-44665 has a CVSS v3.1 base score of 6.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2026-44665?
CVE-2026-44665 is classified under CWE-91: XML Injection (aka Blind XPath Injection) (The product does not properly neutralize special elements that are used in XML, allowing attackers to modify the syntax, content, or commands of the XML before it is processed by an end system.).
How can I check npm dependencies for CVE-2026-44665?
Run the dependency tree command: 'npm ls fast-xml-builder'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-5wm8-gmm8-39j9",
  "modified" : "2026-05-14T20:37:36Z",
  "published" : "2026-05-08T16:29:10Z",
  "aliases" : [ "CVE-2026-44665" ],
  "summary" : "fast-xml-builder allows attribute values with unwanted quotes to bypass malicious or unwanted attributes",
  "details" : "# Summary\nWhen an input data has quotes in attribute values but process entities is not enabled, it breaks the attribute value into multiple attributes. This gives the room for an attacker to insert unwanted attributes to the XML/HTML.\n\n## Detail\n\nMalicious Input\n```\n{\n      a: {\n        \"@_attr\": '\" onClick=\"alert(1)'\n      }\n}\n```\n\nOutput\n```xml\n<a attr=\"\" onClick=\"alert(1)\"></a>\n```\n\n### Workarounds\nIf you're not ignoring attributes then keep processEntities flag true.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "fast-xml-builder"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.1.7"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.1.6"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-builder/security/advisories/GHSA-5wm8-gmm8-39j9"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44665"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-builder"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-611", "CWE-91" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-08T16:29:10Z",
    "nvd_published_at" : "2026-05-13T16:16:59Z"
  }
}