CVE-2026-33993 in locutus
Summary
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.
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Responsible
GitHub_M
Reservation
03/24/2026
Disclosure
03/28/2026
Status
Confirmed
Entries
VulDB provides additional information and datapoints for this CVE:
| ID | Vulnerability | CWE | Exp | Cou | CVE |
|---|---|---|---|---|---|
| 354058 | locutusjs locutus unserialize prototype pollution | 1321 | Not defined | Official fix | CVE-2026-33993 |