Tinyauth: Unauthenticated login attempts can trigger global login lockdown denial of service
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-307.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| tinyauthapp | tinyauth | before 5.1.0 | 5.1.0 | Patch available | CNA |
| — | github.com/steveiliop56/tinyauth (Go) | before 1.0.1-0.20260715123057-dade1e2c8f27 | 1.0.1-0.20260715123057-dade1e2c8f27 | Patch available | GHSA-9xhm-w3wj-xhqh |
- tinyauth Vendortinyauthapp Affected before 5.1.0 Fixed in 5.1.0 Patch available CNA
- github.com/steveiliop56/tinyauth (Go) Vendor— Affected before 1.0.1-0.20260715123057-dade1e2c8f27 Fixed in 1.0.1-0.20260715123057-dade1e2c8f27 Patch available GHSA-9xhm-w3wj-xhqh
Remediation
- Fix · CNA tinyauth (tinyauthapp) Fixed in 5.1.0
- Fix · GHSA-9xhm-w3wj-xhqh github.com/steveiliop56/tinyauth (Go) Fixed in 1.0.1-0.20260715123057-dade1e2c8f27 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-77561
- 2026-10-03 Alias added: GHSA-9xhm-w3wj-xhqh
References
Other 7
- https://github.com/tinyauthapp/tinyauth/security/advisories/GHSA-9xhm-w3wj-xhqh
- https://github.com/tinyauthapp/tinyauth/pull/1008
- https://github.com/tinyauthapp/tinyauth/pull/943
- https://github.com/tinyauthapp/tinyauth/commit/654b5cc436fc67865c1f55edf9ba9fbded50b74f
- https://github.com/tinyauthapp/tinyauth/commit/dade1e2c8f27a23df56ac216dcaf4b37081698e7
- https://github.com/tinyauthapp/tinyauth/releases/tag/v5.1.0
- https://github.com/tinyauthapp/tinyauth
More tinyauthapp vulnerabilities
- TI-2026-54084 Tinyauth: User enumeration attack by timing oracle CVSS 4.0MEDIUM 6.9
- TI-2026-54079 Incorrect authorization in tinyauthapp tinyauth CVSS 3.1HIGH 8.1
Sources
- CVE-2026-77561 · CVE Program
- CVE-2026-77561 · NVD
- FIRST EPSS
- GHSA-9xhm-w3wj-xhqh · GitHub Advisory Database · CC BY 4.0
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