CVE-2026-33993

CVE-2026-33993 · Locutus has Prototype Pollution via __proto__ Key Injection in unserialize()

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 6.9 · Medium · EPSS 0.6% · Fix available

Published

2026-03-27T22:14:03.495Z

Updated

2026-03-30T15:45:18.660Z

Stack: node

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