CVE-2026-33993

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.

Affected Software

VendorProductVersion RangeStatus
locutusjslocutus< 3.0.25affected

Weaknesses

  • CWE-1321: CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: yes
    • Technical Impact: partial

References