CVE-2026-77561 — MEDIUM (5.3)

Vulnerability 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.

CVSS Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

NONE

Availability

LOW

Related Weaknesses (CWE)

CWE-307

References

FAQ

What is CVE-2026-77561?

CVE-2026-77561 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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 MaxLog...

How severe is CVE-2026-77561?

CVE-2026-77561 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-77561?

Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.