CVE-2025-64718
js-yaml has prototype pollution in merge (<<)
- State
- Published
- Severity
- 5.3 Medium
- Published
- Nov 13, 2025
- Updated
- Jan 29, 2026
- Reserved
- Nov 10, 2025
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).
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 5.3 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N | GitHub_M |
Weaknesses
- CWE-1321 Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Products
| Product | Versions |
|---|---|
js-yamlnodeca |
|
References
- https://github.com/nodeca/js-yaml/security/advisories/GHSA-mh29-5h37-fv8m
- https://github.com/nodeca/js-yaml/issues/730#issuecomment-3549635876
- https://github.com/nodeca/js-yaml/commit/383665ff4248ec2192d1274e934462bb30426879
- https://github.com/nodeca/js-yaml/commit/5278870a17454fe8621dbd8c445c412529525266
- https://github.com/advisories/GHSA-mh29-5h37-fv8m
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