CVE-2026-73569: fast-xml-parser Repeated DOCTYPE Declarations Reset Entity Vulnerability

HIGH
Advisory Identifier: GHSA-8r6m-32jq-jx6q
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CWE-776
Published
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.

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
  }
}