Vulnerability Description
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 Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Locutus | Locutus | < 3.0.25 |
Related Weaknesses (CWE)
References
- https://github.com/locutusjs/locutus/commit/345a6211e1e6f939f96a7090bfeff642c9fcPatch
- https://github.com/locutusjs/locutus/pull/597Issue Tracking
- https://github.com/locutusjs/locutus/releases/tag/v3.0.25Release Notes
- https://github.com/locutusjs/locutus/security/advisories/GHSA-4mph-v827-f877ExploitMitigationVendor Advisory
FAQ
What is CVE-2026-33993?
CVE-2026-33993 is a vulnerability with a CVSS score of 9.8 (CRITICAL). 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 deserialize...
How severe is CVE-2026-33993?
CVE-2026-33993 has been rated CRITICAL with a CVSS base score of 9.8/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-33993?
Check the references section above for vendor advisories and patch information. Affected products include: Locutus Locutus.