MEDIUM 5.3
GHSA-mh29-5h37-fv8m
js-yaml has prototype pollution in merge (<<)
Details
### 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
Are you affected?
Enter the version of the package you're using.
Affected packages
References
- https://github.com/nodeca/js-yaml/security/advisories/GHSA-mh29-5h37-fv8m [WEB]
- https://nvd.nist.gov/vuln/detail/CVE-2025-64718 [ADVISORY]
- https://github.com/nodeca/js-yaml/issues/730#issuecomment-3549635876 [WEB]
- https://github.com/nodeca/js-yaml/commit/383665ff4248ec2192d1274e934462bb30426879 [WEB]
- https://github.com/nodeca/js-yaml/commit/5278870a17454fe8621dbd8c445c412529525266 [WEB]
- https://github.com/advisories/GHSA-mh29-5h37-fv8m [ADVISORY]
- https://github.com/nodeca/js-yaml [PACKAGE]