CVE-2026-33993
Locutus brings stdlibs of other programming languages to JavaScript for educational purposes. Prior to version 3.0.25, the `unserialize()` function in `locutus/php/var/unserialize` assigns deserialized keys to plain objects via bracket notation without filtering the `__proto__` key. When a PHP serialized payload contains `__proto__` as an array or object key, JavaScript's `__proto__` setter is invoked, replacing the deserialized object's prototype with attacker-controlled content. This enables property injection, for...in propagation of injected properties, and denial of service via built-in method override. This is distinct from the previously reported prototype pollution in `parse_str` (GHSA-f98m-q3hr-p5wq, GHSA-rxrv-835q-v5mh) — `unserialize` is a different function with no mitigation applied. Version 3.0.25 patches the issue.
- Score
- CVSS 3.1 9.8 Critical
- Status
- Analyzed - security-advisories@github.com
- Published
- 2026-03-27
- Last modified
- 2026-10-26
- Weaknesses
- CWE-1321
Affected products
References
- https://github.com/locutusjs/locutus/security/advisories/GHSA-4mph-v827-f877
- https://github.com/locutusjs/locutus/pull/597
- https://github.com/locutusjs/locutus/commit/345a6211e1e6f939f96a7090bfeff642c9fcf9e4
- https://github.com/locutusjs/locutus/releases/tag/v3.0.25
