CVE-2026-77561

5.3 MEDIUMpublic exploit available

Published 2026-09-21 · Updated 2026-09-21

AI risk analysis

Summary: The flaw allows unauthenticated attackers to trigger a global login lockdown by sending POST requests with nonexistent usernames, leading to HTTP 429 rate limiting for legitimate users.
Exploitability: Exploitation is relatively easy as it requires sending 257 distinct non-existent usernames. Precondition: The target system must be running an affected version of Tinyauth before 5.1.0.
Blast radius: If exploited, the impact could significantly disrupt user access for up to 300 seconds, affecting legitimate users until the lockdown is lifted.
Prioritized remediation: Upgrade to Tinyauth version 5.1.0 or later to mitigate this vulnerability.

auth-bypassrate-limitingweb

Analysis generated locally by qwen2.5:7b-instruct (no data left the box). AI-assisted — verify against primary sources before acting.

NVD 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 vector

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

Weaknesses

CWE-307

Public exploit & PoC references

All references

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

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