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[ CVE-2026-77561 · Published 21 Sep 2026 ]

Tinyauth: Unauthenticated login attempts can trigger global login lockdown denial of service

CVSS 5.3 EPSS <1%Fix available

[ Why it matters ]Priority signals

  • Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

Tinyauth is an authentication and authorization server. Prior to 5.1.0, an unauthenticated remote attacker can send POST /api/user/login requests with 257 distinct nonexistent usernames to fill MaxLoginAttemptRecords and activate a global login lockdown. internal/controller/user_controller.go loginHandler passes each attacker-controlled identifier to internal/service/auth_service.go RecordLoginAttempt, which invokes lockdownMode after the map reaches its cap. IsAccountLocked checks that global state before validating unrelated accounts, causing valid users to receive HTTP 429 until auth.loginTimeout expires, approximately 300 seconds by default. The attack can be repeated, but existing authenticated sessions are not invalidated. This issue is fixed in version 5.1.0.

[ Fixes ]Fixes and patches

[ Packages ]Affected open-source packages

  • github.com/steveiliop56/tinyauth goAffected < 1.0.1-0.20260715123057-dade1e2c8f27 · fixed in 1.0.1-0.20260715123057-dade1e2c8f27 · GHSA-9xhm-w3wj-xhqh

[ References ]References