Simple JWT Login <= 3.6.6 - Authenticated (Subscriber+) Authentication Bypass to Privilege Escalation via 'payload' Parameter

Summary

The Simple JWT Login – Allows you to use JWT on REST endpoints. plugin for WordPress is vulnerable to Authentication Bypass to Privilege Escalation in all versions up to, and including, 3.6.6 via the `payload` parameter. The vulnerability exists because `AuthenticateService::generatePayload()` only overwrites JWT payload keys whose names appear in the admin-configured `jwt_payload` list — leaving any attacker-supplied identity claims such as `email`, `id`, or `username` intact and signed into the JWT with the site's HS256 secret. This makes it possible for authenticated attackers, with subscriber-level access and above, to escalate their privileges to that of an Administrator by injecting a target administrator's email address into the `payload` parameter at the `/wp-json/simple-jwt-login/v1/auth` endpoint, then redeeming the resulting JWT at the `/autologin` endpoint to obtain a fully authenticated session as that administrator.

Timeline

1. Jul 11, 2026, 3:44 AM UTCCVE published
2. Jul 13, 2026, 5:36 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Jul 13, 2026, 5:37 PM UTCRecord last updated

Affected versions

• nicu_m Simple JWT Login – Allows you to use JWT on REST endpoints.

  through 3.6.6

References 6