CVE-2026-77560 Tinyauth: forward-auth per-app ACL is matched case-sensitively against the (case-insensitive) hostname, letting an authenticated user reach apps they are not on the allowlist for
An authenticated user can bypass per-app access controls by using a differently cased hostname, gaining unauthorized access to restricted applications.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-77560?
CVE-2026-77560 is a high-severity authentication bypass vulnerability in tinyauthapp tinyauth, published on 21 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Tinyauth is an authentication and authorization server. Prior to 5.1.2, Tinyauth compares forwarded hostnames case-sensitively while reverse proxies route equivalent hostnames case-insensitively, allowing an authenticated low-privilege user to bypass per-app access controls with a differently cased hostname. The lookup in internal/service/access_controls_service.go through lookupStaticACLs and GetAccessControls, and the Docker-label fallback in internal/service/docker_service.go through GetLabels, can miss the configured app and return an empty access-control object. internal/controller/proxy_controller.go proxyHandler then treats the empty user, group, OAuth, LDAP, and IP restrictions as permissive and returns an authenticated result for an app that should exclude the user. Unauthenticated users remain subject to login, and global login-time allowlists are not bypassed. This issue is fixed in version 5.1.2.
Which versions are affected by CVE-2026-77560?
3 open source packages ship an affected version, including github.com/tinyauthapp/tinyauth.
| Package | Affected | Fixed in |
|---|---|---|
github.com/tinyauthapp/tinyauth Go | All versions | 1.0.1-0.20260720133915-80bc87188ec3 |
github.com/tinyauthapp/tinyauth Go | All versions | 1.0.1-0.20260720133915-80bc87188ec3 |
github.com/tinyauthapp/tinyauth Go | All versions | 1.0.1-0.20260720133915-80bc87188ec3 |
How do I fix CVE-2026-77560?
Upgrade github.com/tinyauthapp/tinyauth to 1.0.1-0.20260720133915-80bc87188ec3 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-77560 being exploited?
There is no known exploitation of CVE-2026-77560 in the wild and no public exploit code.
Sources
Also known as GHSA-328g-jx67-v94g, GO-2026-6552.