CVE-2026-77561

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

A remote unauthenticated attacker who can reach Tinyauth's login endpoint can temporarily deny login for unrelated valid users by sending a small number of login attempts using unique nonexistent usernames.

With default configuration, the global lockdown lasts 300 seconds. The attack does not invalidate existing sessions, but users who need to log in during the lockdown window receive rate-limit responses even when providing valid credentials.

This affects availability of local login and any flow that depends on the same account-lock check. The issue is especially relevant for internet-exposed Tinyauth deployments where /api/user/login is reachable.

Suggested remediation: do not enter global lockdown because of attacker-controlled unknown usernames. Use bounded LRU eviction for old login-attempt records instead of global lockout; consider rate limiting by client IP plus normalized username; avoid counting unlimited nonexistent usernames toward a global security state. If a global safety mode is desired, require stronger signals such as source-based thresholds rather than only distinct username count.

CVE-2026-77561 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.0.1-0.20260715123057-dade1e2c8f27); upgrading removes the vulnerable code path.

Kodem intelligence

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1. What is CVE-2026-77561? CVE-2026-77561 is a medium-severity security vulnerability in github.com/steveiliop56/tinyauth (go), affecting versions < 1.0.1-0.20260715123057-dade1e2c8f27. It is fixed in 1.0.1-0.20260715123057-dade1e2c8f27.
2. How severe is CVE-2026-77561? CVE-2026-77561 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/steveiliop56/tinyauth are affected by CVE-2026-77561? github.com/steveiliop56/tinyauth (go) versions < 1.0.1-0.20260715123057-dade1e2c8f27 is affected.
4. Is there a fix for CVE-2026-77561? Yes. CVE-2026-77561 is fixed in 1.0.1-0.20260715123057-dade1e2c8f27. Upgrade to this version or later.
5. Is CVE-2026-77561 exploitable, and should I be worried? Whether CVE-2026-77561 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-77561 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-77561? Upgrade github.com/steveiliop56/tinyauth to 1.0.1-0.20260715123057-dade1e2c8f27 or later.

Other vulnerabilities in github.com/steveiliop56/tinyauth