CVE-2023-26920: Fast xml parser Fast-xml-parser Vulnerable To Prototype Pollution Vulnerability

MODERATE
Advisory Identifier: GHSA-x3cc-x39p-42qx
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CVSS 6.5
CWE-1321
Published
Advisory Summary

CVE-2023-26920 is a MODERATE (CVSS 6.5) fast-xml-parser vulnerable to prototype pollution vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Fast xml parser libraries in the npm ecosystem. The issue involves fast-xml-parser vulnerable to prototype pollution through tag or attribute name. Remediation is available by upgrading affected packages to version 4.1.2.

CVE-2023-26920 at a Glance

CVE Identifier CVE-2023-26920
GHSA Identifier GHSA-x3cc-x39p-42qx
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product Fast xml parser
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 6.5

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

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

How to Fix CVE-2023-26920

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: 4.1.2 
npm install fast-xml-parser@4.1.2
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-2023-26920, 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 4.1.2), 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-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution'), where the product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. 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 As a part of this vulnerability, user was able to se code using `__proto__` as a tag or attribute name. ```js const { XMLParser, XMLBuilder, XMLValidator} = require("fast-xml-parser"); let XMLdata = "<__proto__><polluted>hacked</polluted></__proto__>" const parser = new XMLParser(); let jObj = parser.parse(XMLdata); console.log(jObj.polluted) // should return hacked ``` ### Patches The problem has been patched in v4.1.2 ### Workarounds User can check for "__proto__" in the XML string before parsing it to the parser. ### References https://gist.github.com/Sudistark/a5a45bd0804d522a1392cb5023aa7ef7

CVE-2023-26920 Affected Fast xml parser Versions

1 component(s)
Fixed Versions:
4.1.2
Product / Package Ecosystem Affected Versions Fixed Version
fast-xml-parser
npm/fast-xml-parser
npm
< 4.1.2
4.1.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-x3cc-x39p-42qx
NVD — CVE-2023-26920 NVD
https://nvd.nist.gov/vuln/detail/CVE-2023-26920
Security Fix Commit FIX COMMIT
https://github.com/NaturalIntelligence/fast-xml-parser/commit/2b032a4f799c63d83991e4f992f1c68e4dd05804
Fast xml parser Source Repository REPOSITORY
https://gist.github.com/Sudistark/a5a45bd0804d522a1392cb5023aa7ef7
Fast xml parser Source Repository REPOSITORY
https://github.com/NaturalIntelligence/fast-xml-parser
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-793h-6f7r-6qvm

Frequently Asked Questions

What is CVE-2023-26920?
CVE-2023-26920 is a security vulnerability in Fast xml parser involving fast-xml-parser vulnerable to Prototype Pollution through tag or attribute name under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which Fast xml parser versions are affected?
Affected versions include releases prior to 4.1.2 across affected packages: fast-xml-parser.
What version fixes CVE-2023-26920?
Upgrading to 4.1.2 (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 4.1.2. Upgrade your dependency to 4.1.2 or later.
What is the CVSS score of CVE-2023-26920?
CVE-2023-26920 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2023-26920?
CVE-2023-26920 is classified under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.).
How can I check npm dependencies for CVE-2023-26920?
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-x3cc-x39p-42qx",
  "modified" : "2023-12-14T22:27:59Z",
  "published" : "2023-06-13T12:44:34Z",
  "aliases" : [ "CVE-2023-26920" ],
  "summary" : "fast-xml-parser vulnerable to Prototype Pollution through tag or attribute name",
  "details" : "### Impact\nAs a part of this vulnerability, user was able to se code using `__proto__` as a tag or attribute name.\n\n```js\nconst { XMLParser, XMLBuilder, XMLValidator} = require(\"fast-xml-parser\");\n\nlet XMLdata = \"<__proto__><polluted>hacked</polluted></__proto__>\"\n\nconst parser = new XMLParser();\nlet jObj = parser.parse(XMLdata);\n\nconsole.log(jObj.polluted) // should return hacked\n``` \n\n### Patches\nThe problem has been patched in v4.1.2\n\n### Workarounds\nUser can check for \"__proto__\" in the XML string before parsing it to the parser.\n\n### References\nhttps://gist.github.com/Sudistark/a5a45bd0804d522a1392cb5023aa7ef7\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "fast-xml-parser"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.1.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-x3cc-x39p-42qx"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-26920"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser/commit/2b032a4f799c63d83991e4f992f1c68e4dd05804"
  }, {
    "type" : "WEB",
    "url" : "https://gist.github.com/Sudistark/a5a45bd0804d522a1392cb5023aa7ef7"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/NaturalIntelligence/fast-xml-parser"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-793h-6f7r-6qvm"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-06-13T12:44:34Z",
    "nvd_published_at" : "2023-12-12T17:15:07Z"
  }
}