Vulnerabilities in pkg:npm/fast-xml-parser

PACKAGE
Advisory Identifier: GHSA-8r6m-32jq-jx6q
Share
Advisory Summary

CVE-2026-73569 is a HIGH repeated doctype declarations reset entity vulnerability (CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')) affecting fast-xml-parser libraries in the npm ecosystem. The issue involves repeated doctype declarations reset entity expansion limits. Remediation is available by upgrading affected packages to version 5.10.1.

12 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:npm/fast-xml-parser

12 Known Advisory Record(s)

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

Advisory ID CVE / NVD Severity Summary
GHSA-8r6m-32jq-jx6q CVE-2026-73569 HIGH fast-xml-parser: Repeated DOCTYPE declarations reset entity expansion limits
GHSA-gh4j-gqv2-49f6 CVE-2026-41650 MODERATE fast-xml-parser XMLBuilder: XML Comment and CDATA Injection via Unescaped Delimiters
GHSA-jp2q-39xq-3w4g CVE-2026-33349 MODERATE Entity Expansion Limits Bypassed When Set to Zero Due to JavaScript Falsy Evaluation in fast-xml-parser
GHSA-8gc5-j5rx-235r CVE-2026-33036 HIGH fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)
GHSA-6w63-h3fj-q4vw CVE-2023-34104 HIGH fast-xml-parser vulnerable to Regex Injection via Doctype Entities
GHSA-fj3w-jwp8-x2g3 CVE-2026-27942 LOW fast-xml-parser has stack overflow in XMLBuilder with preserveOrder
GHSA-m7jm-9gc2-mpf2 CVE-2026-25896 CRITICAL fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names
GHSA-jmr7-xgp7-cmfj CVE-2026-26278 HIGH fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)
GHSA-37qj-frw5-hhjh CVE-2026-25128 HIGH fast-xml-parser has RangeError DoS Numeric Entities Bug
GHSA-mpg4-rc92-vx8v CVE-2024-41818 HIGH fast-xml-parser vulnerable to ReDOS at currency parsing
GHSA-x3cc-x39p-42qx CVE-2023-26920 MODERATE fast-xml-parser vulnerable to Prototype Pollution through tag or attribute name
GHSA-gpv5-7x3g-ghjv - LOW fast-xml-parser regex vulnerability patch could be improved from a safety perspective

CVE-2026-73569 at a Glance

CVE Identifier CVE-2026-73569
GHSA Identifier GHSA-8r6m-32jq-jx6q
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
Affected Product fast-xml-parser
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-73569

To remediate this vulnerability, upgrade all affected fast-xml-parser 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-parser fixed: 5.10.1 
npm install fast-xml-parser@5.10.1
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-parser

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-73569, inspect your project dependencies using npm:

npm ls fast-xml-parser

Analyze the terminal output to locate any version of fast-xml-parser in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.10.1), your application is affected.

Note: The npm ls fast-xml-parser 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-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion'), where the product uses xml documents and allows their structure to be defined with a document type definition (dtd), but it does not properly control the number of recursive definitions of entities. In fast-xml-parser, 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

### Impact `fast-xml-parser` processes multiple "DOCTYPE" declarations within a single XML document. Each declaration passes its entities to `@nodable/entities` through `addInputEntities()`. `addInputEntities()` resets the entity expansion counters every time it is called. An attacker can therefore insert additional DOCTYPE declarations to repeatedly reset maxTotalExpansions and maxExpandedLength during one parse operation. This allows a crafted XML document to exceed the configured entity-expansion limits and can cause excessive CPU use, event-loop blocking, memory exhaustion, and process termination. ### Workarounds - Manually check if multiple DOCTYPEs are not present in input contents - Update to v5.10.1 - Keep `processEntity` flag off

CVE-2026-73569 Affected fast-xml-parser Versions

1 component(s)
Fixed Versions:
5.10.1
Product / Package Ecosystem Affected Versions Fixed Version
fast-xml-parser
npm/fast-xml-parser
npm
≥ 5.9.3
< 5.10.1
5.10.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8r6m-32jq-jx6q
Security Fix Commit FIX COMMIT
https://github.com/NaturalIntelligence/fast-xml-parser/commit/4e546e03987662de5495d050b5fba26bea65383f
fast-xml-parser Source Repository REPOSITORY
https://github.com/NaturalIntelligence/fast-xml-parser
fast-xml-parser Release RELEASE
https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.10.1

Frequently Asked Questions

What is CVE-2026-73569?
CVE-2026-73569 is a security vulnerability in fast-xml-parser involving Repeated DOCTYPE declarations reset entity expansion limits under CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion').
Which fast-xml-parser versions are affected?
Affected versions include releases prior to 5.10.1 across affected packages: fast-xml-parser.
What version fixes CVE-2026-73569?
Upgrading to 5.10.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is fast-xml-parser affected?
Yes, fast-xml-parser is affected in releases prior to 5.10.1. Upgrade your dependency to 5.10.1 or later.
What CWE is associated with CVE-2026-73569?
CVE-2026-73569 is classified under CWE-776: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion') (The product uses XML documents and allows their structure to be defined with a Document Type Definition (DTD), but it does not properly control the number of recursive definitions of entities.).
How can I check npm dependencies for CVE-2026-73569?
Run the dependency tree command: 'npm ls fast-xml-parser'. 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-8r6m-32jq-jx6q",
  "modified" : "2026-08-13T17:45:28Z",
  "published" : "2026-07-21T22:06:36Z",
  "aliases" : [ "CVE-2026-73569" ],
  "summary" : "fast-xml-parser: Repeated DOCTYPE declarations reset entity expansion limits",
  "details" : "### Impact\n`fast-xml-parser` processes multiple \"DOCTYPE\" declarations within a single XML document. Each declaration passes its entities to `@nodable/entities` through `addInputEntities()`.\n\n`addInputEntities()` resets the entity expansion counters every time it is called. An attacker can therefore insert additional DOCTYPE declarations to repeatedly reset maxTotalExpansions and maxExpandedLength during one parse operation.\n\nThis allows a crafted XML document to exceed the configured entity-expansion limits and can cause excessive CPU use, event-loop blocking, memory exhaustion, and process termination.\n\n### Workarounds\n- Manually check if multiple DOCTYPEs are not present in input contents\n- Update to v5.10.1\n- Keep `processEntity` flag off",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "fast-xml-parser"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.9.3"
      }, {
        "fixed" : "5.10.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8r6m-32jq-jx6q"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser/commit/4e546e03987662de5495d050b5fba26bea65383f"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.10.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-776" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-21T22:06:36Z",
    "nvd_published_at" : null
  }
}