# 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.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Sep 2026
- **Updated:** 21 Sep 2026
- **Also known as:** GHSA-328g-jx67-v94g, GO-2026-6552

## 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.

Weakness: CWE-863 (Incorrect Authorization), CWE-636 (Not Failing Securely), CWE-178 (Improper Handling of Case Sensitivity)

## Which versions are affected by CVE-2026-77560?

3 open source packages ship an affected version, including github.com/tinyauthapp/tinyauth.


| Package | Ecosystem | 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.

## Is CVE-2026-77560 being exploited?

There is no known exploitation of CVE-2026-77560 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77560 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-77560 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/tinyauthapp/tinyauth (Go): affected all versions; fixed in 1.0.1-0.20260720133915-80bc87188ec3
- github.com/tinyauthapp/tinyauth (Go): affected all versions; fixed in 1.0.1-0.20260720133915-80bc87188ec3
- github.com/tinyauthapp/tinyauth (Go): affected all versions; fixed in 1.0.1-0.20260720133915-80bc87188ec3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77560/ (Markdown: https://insights.sbomify.com/CVE-2026-77560/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77560
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77560
- OSV: https://osv.dev/vulnerability/CVE-2026-77560

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77560/
Summaries are generated and may contain mistakes; the official description above is the record.