CVE-2025-64718: Js yaml Js-yaml Has Prototype Pollution Vulnerability

MODERATE
Advisory Identifier: GHSA-mh29-5h37-fv8m
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CVSS 5.3
CWE-1321
Published
Advisory Summary

CVE-2025-64718 is a MODERATE (CVSS 5.3) js-yaml has prototype pollution vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting Js yaml libraries in the npm ecosystem. The issue involves js-yaml has prototype pollution in merge (<<). Remediation is available by upgrading affected packages to version 4.1.1, 3.14.2.

CVE-2025-64718 at a Glance

CVE Identifier CVE-2025-64718
GHSA Identifier GHSA-mh29-5h37-fv8m
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product Js yaml
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.3

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:L/A:N).

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 Low (I:L)
Availability None (A:N)

How to Fix CVE-2025-64718

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

js-yaml fixed: 4.1.1 
npm install js-yaml@4.1.1
js-yaml fixed: 3.14.2 
npm install js-yaml@3.14.2
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 js-yaml

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2025-64718, inspect your project dependencies using npm:

npm ls js-yaml

Analyze the terminal output to locate any version of Js yaml in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.1.1), your application is affected.

Note: The npm ls js-yaml 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 Js yaml, 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 In js-yaml 4.1.0, 4.0.0, and 3.14.1 and below, it's possible for an attacker to modify the prototype of the result of a parsed yaml document via prototype pollution (`__proto__`). All users who parse untrusted yaml documents may be impacted. ### Patches Problem is patched in js-yaml 4.1.1 and 3.14.2. ### Workarounds You can protect against this kind of attack on the server by using `node --disable-proto=delete` or `deno` (in Deno, pollution protection is on by default). ### References https://cheatsheetseries.owasp.org/cheatsheets/Prototype_Pollution_Prevention_Cheat_Sheet.html

CVE-2025-64718 Affected Js yaml Versions

2 component(s)
Fixed Versions:
4.1.13.14.2
Product / Package Ecosystem Affected Versions Fixed Version
js-yaml
npm/js-yaml
npm
≥ 4.0.0
< 4.1.1
4.1.1
js-yaml
npm/js-yaml
npm
< 3.14.2
3.14.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/nodeca/js-yaml/security/advisories/GHSA-mh29-5h37-fv8m
NVD — CVE-2025-64718 NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-64718
Js yaml Source Repository REPOSITORY
https://github.com/nodeca/js-yaml/issues/730#issuecomment-3549635876
Security Fix Commit FIX COMMIT
https://github.com/nodeca/js-yaml/commit/383665ff4248ec2192d1274e934462bb30426879
Security Fix Commit FIX COMMIT
https://github.com/nodeca/js-yaml/commit/5278870a17454fe8621dbd8c445c412529525266
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-mh29-5h37-fv8m
Js yaml Source Repository REPOSITORY
https://github.com/nodeca/js-yaml

Frequently Asked Questions

What is CVE-2025-64718?
CVE-2025-64718 is a security vulnerability in Js yaml involving js-yaml has prototype pollution in merge (<<) under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which Js yaml versions are affected?
Affected versions include releases prior to 4.1.1, 3.14.2 across affected packages: js-yaml.
What version fixes CVE-2025-64718?
Upgrading to 4.1.1, 3.14.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is js-yaml affected?
Yes, js-yaml is affected in releases prior to 4.1.1, 3.14.2. Upgrade your dependency to 4.1.1, 3.14.2 or later.
What is the CVSS score of CVE-2025-64718?
CVE-2025-64718 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2025-64718?
CVE-2025-64718 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-2025-64718?
Run the dependency tree command: 'npm ls js-yaml'. 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-mh29-5h37-fv8m",
  "modified" : "2026-01-31T03:32:42Z",
  "published" : "2025-11-14T14:29:48Z",
  "aliases" : [ "CVE-2025-64718" ],
  "summary" : "js-yaml has prototype pollution in merge (<<)",
  "details" : "### Impact\n\nIn js-yaml 4.1.0, 4.0.0, and 3.14.1 and below, it's possible for an attacker to modify the prototype of the result of a parsed yaml document via prototype pollution (`__proto__`). All users who parse untrusted yaml documents may be impacted.\n\n### Patches\n\nProblem is patched in js-yaml 4.1.1 and 3.14.2.\n\n### Workarounds\n\nYou can protect against this kind of attack on the server by using `node --disable-proto=delete` or `deno` (in Deno, pollution protection is on by default).\n\n### References\n\nhttps://cheatsheetseries.owasp.org/cheatsheets/Prototype_Pollution_Prevention_Cheat_Sheet.html",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "js-yaml"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.1.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "js-yaml"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.14.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/nodeca/js-yaml/security/advisories/GHSA-mh29-5h37-fv8m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-64718"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nodeca/js-yaml/issues/730#issuecomment-3549635876"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nodeca/js-yaml/commit/383665ff4248ec2192d1274e934462bb30426879"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nodeca/js-yaml/commit/5278870a17454fe8621dbd8c445c412529525266"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-mh29-5h37-fv8m"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nodeca/js-yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-11-14T14:29:48Z",
    "nvd_published_at" : "2025-11-13T16:15:57Z"
  }
}