---
id: "CVE-2026-77560"
kind: "vulnerability"
aliases: ["CVE-2026-77560", "GHSA-328g-jx67-v94g", "GO-2026-6552"]
title: "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 in github.com/tinyauthapp/tinyauth"
severity: "high"
cvss: 8.1
epss: 0.00612
exploited: false
status: "open"
category: "package"
products: [{"name": "github.com/tinyauthapp/tinyauth", "fixed": ["1.0.1-0.20260720133915-80bc87188ec3"], "affected": "< 1.0.1-0.20260720133915-80bc87188ec3", "ecosystem": "go"}]
ecosystems: ["go"]
tags: ["docker", "forward-auth", "package", "self-hosted", "tinyauth"]
not_affected_if: ["no-per-app-acls", "version-5.1.2-or-later"]
published_at: "2026-09-21T17:18:52+00:00"
first_seen_at: "2026-10-23T19:13:08+00:00"
updated_at: "2026-10-23T21:45:36+00:00"
sources: [{"source": "govuln", "url": "https://pkg.go.dev/vuln/GO-2026-6552", "first_seen_at": "2026-10-23T19:13:08+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-77560", "first_seen_at": "2026-10-23T19:13:43+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-77560", "first_seen_at": "2026-10-23T19:35:23+00:00"}]
---

# 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 in github.com/tinyauthapp/tinyauth

Tinyauth matches per-app access control lists case-sensitively against a hostname that is case-insensitive, so a differently cased hostname can return an empty access-control object. An authenticated low-privilege user can then reach apps they are not on the allowlist for.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- go:github.com/tinyauthapp/tinyauth affected < 1.0.1-0.20260720133915-80bc87188ec3 fixed 1.0.1-0.20260720133915-80bc87188ec3

## How to check

Confirm the running Tinyauth version is below 5.1.2. For Go builds, run go list -m github.com/tinyauthapp/tinyauth.

## Fix

Upgrade Tinyauth to 5.1.2 or later. For the Go module, use 1.0.1-0.20260720133915-80bc87188ec3 or later.

## Timeline

- 2026-10-23T19:13:08+00:00 govuln https://pkg.go.dev/vuln/GO-2026-6552
- 2026-10-23T19:13:43+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-77560
- 2026-10-23T19:35:23+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-77560

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_