CVE-2023-34104: Fast xml parser Fast-xml-parser Vulnerable To Regex Injection Vulnerability

HIGH
Advisory Identifier: GHSA-6w63-h3fj-q4vw
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CVSS 7.5
CWE-400 CWE-1333
Published
Advisory Summary

CVE-2023-34104 is a HIGH (CVSS 7.5) fast-xml-parser vulnerable to regex injection vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Fast xml parser libraries in the npm ecosystem. The issue involves fast-xml-parser vulnerable to regex injection via doctype entities. Remediation is available by upgrading affected packages to version 4.2.4.

CVE-2023-34104 at a Glance

CVE Identifier CVE-2023-34104
GHSA Identifier GHSA-6w63-h3fj-q4vw
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Fast xml parser
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.5

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:N/S:U/C:N/I:N/A:H).

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

How to Fix CVE-2023-34104

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: 4.2.4 
npm install fast-xml-parser@4.2.4
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-2023-34104, 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 4.2.4), 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-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. 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" allows special characters in entity names, which are not escaped or sanitized. Since the entity name is used for creating a regex for searching and replacing entities in the XML body, an attacker can abuse it for DoS attacks. By crafting an entity name that results in an intentionally bad performing regex and utilizing it in the entity replacement step of the parser, this can cause the parser to stall for an indefinite amount of time. ### Patches The problem has been resolved in v4.2.4 ### Workarounds Avoid using DOCTYPE parsing by `processEntities: false` option.

CVE-2023-34104 Affected Fast xml parser Versions

1 component(s)
Fixed Versions:
4.2.4
Product / Package Ecosystem Affected Versions Fixed Version
fast-xml-parser
npm/fast-xml-parser
npm
≥ 4.1.3
< 4.2.4
4.2.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-6w63-h3fj-q4vw
NVD — CVE-2023-34104 NVD
https://nvd.nist.gov/vuln/detail/CVE-2023-34104
Security Fix Commit FIX COMMIT
https://github.com/NaturalIntelligence/fast-xml-parser/commit/39b0e050bb909e8499478657f84a3076e39ce76c
Security Fix Commit FIX COMMIT
https://github.com/NaturalIntelligence/fast-xml-parser/commit/a4bdced80369892ee413bf08e28b78795a2b0d5b
Fast xml parser Source Repository REPOSITORY
https://github.com/NaturalIntelligence/fast-xml-parser

Frequently Asked Questions

What is CVE-2023-34104?
CVE-2023-34104 is a security vulnerability in Fast xml parser involving fast-xml-parser vulnerable to Regex Injection via Doctype Entities under CWE-400: Uncontrolled Resource Consumption.
Which Fast xml parser versions are affected?
Affected versions include releases prior to 4.2.4 across affected packages: fast-xml-parser.
What version fixes CVE-2023-34104?
Upgrading to 4.2.4 (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 4.2.4. Upgrade your dependency to 4.2.4 or later.
What is the CVSS score of CVE-2023-34104?
CVE-2023-34104 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2023-34104?
CVE-2023-34104 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check npm dependencies for CVE-2023-34104?
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-6w63-h3fj-q4vw",
  "modified" : "2026-03-09T15:58:38Z",
  "published" : "2023-06-06T17:33:13Z",
  "aliases" : [ "CVE-2023-34104" ],
  "summary" : "fast-xml-parser vulnerable to Regex Injection via Doctype Entities",
  "details" : "### Impact\n\"fast-xml-parser\" allows special characters in entity names, which are not escaped or sanitized. Since the entity name is used for creating a regex for searching and replacing entities in the XML body, an attacker can abuse it for DoS attacks. By crafting an entity name that results in an intentionally bad performing regex and utilizing it in the entity replacement step of the parser, this can cause the parser to stall for an indefinite amount of time.\n\n### Patches\nThe problem has been resolved in v4.2.4\n\n### Workarounds\nAvoid using DOCTYPE parsing by `processEntities: false` option.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "fast-xml-parser"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.1.3"
      }, {
        "fixed" : "4.2.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-6w63-h3fj-q4vw"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-34104"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser/commit/39b0e050bb909e8499478657f84a3076e39ce76c"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser/commit/a4bdced80369892ee413bf08e28b78795a2b0d5b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333", "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-06-06T17:33:13Z",
    "nvd_published_at" : "2023-06-06T18:15:11Z"
  }
}