CVE-2025-64718: js-yaml Prototype Pollution — Fix

Description

js-yaml is a JavaScript YAML parser and dumper. In js-yaml before 4.1.1 and 3.14.2, 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. The problem is patched in js-yaml 4.1.1 and 3.14.2. Users 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).

Is your site exposed to CVE-2025-64718?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Weakness Type (CWE)

CWE-1321 CWE-1321

Affected Products

Vendor	Product	Versions
nodeca	js-yaml	< 3.14.2
nodeca	js-yaml	4.0.0 — 4.1.1

References

Advisories & Patches

https://github.com/nodeca/js-yaml/commit/383665ff4248ec2192d1274e934462bb30426879 https://github.com/nodeca/js-yaml/commit/5278870a17454fe8621dbd8c445c412529525266 https://github.com/nodeca/js-yaml/security/advisories/GHSA-mh29-5h37-fv8m https://github.com/advisories/GHSA-mh29-5h37-fv8m

Other References

https://github.com/nodeca/js-yaml/issues/730#issuecomment-3549635876

Frequently Asked Questions

What is CVE-2025-64718? +

js-yaml is a JavaScript YAML parser and dumper. In js-yaml before 4.1.1 and 3.14.2, 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. The problem is patched in js-yaml 4.1.1 and 3.14.2. Users 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). It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2025-64718? +

CVE-2025-64718 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-64718? +

CVE-2025-64718 affects products from nodeca, specifically: js-yaml. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-64718? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-27597

Vue I18n is the internationalization plugin for Vue.js. @intlify/message-resolver and @intlify/vue-i18n-core are vulnerable to Prototype Pollution through the entry function: …

CVE-2025-32014

estree-util-value-to-estree converts a JavaScript value to an ESTree expression. When generating an ESTree from a value with a property named …

CVE-2025-48054

Radashi is a TypeScript utility toolkit. Prior to version 12.5.1, the set function within the Radashi library is vulnerable to …

CVE-2025-8101

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') vulnerability in Linkify (linkifyjs) allows XSS Targeting HTML Attributes and Manipulating …

CVE-2025-34146

A prototype pollution vulnerability exists in @nyariv/sandboxjs versions <= 0.8.23, allowing attackers to inject arbitrary properties into Object.prototype via crafted …

CVE-2025-55164

content-security-policy-parser parses content security policy directives. A prototype pollution vulnerability exists in versions 0.5.0 and earlier, wherein if a policy …

CVE-2025-64718