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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

• CVE-2026-77561: 0.60% estimated exploitation activity in the next 30 days; percentile 48.75 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Tinyauth's login rate-limit bookkeeping can enter a global lockdown mode when its in-memory login-attempt map reaches 256 distinct identifiers. Because unauthenticated POST /api/user/login requests for unknown usernames are recorded in this same map, a remote unauthenticated attacker can submit 257 unique bogus usernames and cause valid credentials for unrelated users to be treated as locked until auth.loginTimeout expires. This was confirmed against the stable v5.0.7 release. With default configuration, auth.loginTimeout is 300 seconds and auth.loginMaxRetries is 3, so the denial lasts about 5 minutes and can be repeated. Details In stable v5.0.7, the login endpoint is registered at internal/controller/usercontroller.go:45 and accepts unauthenticated JSON credentials in loginHandler at internal/controller/usercontroller.go:50. Before validating credentials, it calls controller.auth.IsAccountLocked(req.Username) at internal/controller/usercontroller.go:65. When a username…

Published by the source

22 Sep 2026, 20:37 UTC

Last modified by the source

1 Oct 2026, 20:45 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9xhm-w3wj-xhqh

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6564

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9xhm-w3wj-xhqh

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# Patch Next advisory brief: CVE-2026-77561

Advisory: Tinyauth: Unauthenticated login attempts can trigger global login lockdown denial of service
IDs: CVE-2026-77561, GHSA-9xhm-w3wj-xhqh
Record: https://patchnext.com/advisories/cve-2026-77561 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/tinyauthapp/tinyauth 1.0.1-0.20260715123057-dade1e2c8f27; github.com/steveiliop56/tinyauth 1.0.1-0.20260715123057-dade1e2c8f27. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/tinyauthapp/tinyauth: affected < 1.0.1-0.20260715123057-dade1e2c8f27; fixed in 1.0.1-0.20260715123057-dade1e2c8f27
- Go github.com/steveiliop56/tinyauth: affected < 1.0.1-0.20260715123057-dade1e2c8f27; fixed in 1.0.1-0.20260715123057-dade1e2c8f27

## Suggested inspection (read-only)
- Go github.com/tinyauthapp/tinyauth: check the installed version with your package manager.
- Go github.com/steveiliop56/tinyauth: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/tinyauthapp/tinyauth, github.com/steveiliop56/tinyauth.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9xhm-w3wj-xhqh (OSV record GHSA-9xhm-w3wj-xhqh lists affected ranges: Go github.com/steveiliop56/tinyauth >=0 <1.0.1-0.20260715123057-dade1e2c8f27 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6564 (OSV record GO-2026-6564 lists affected ranges: Go github.com/tinyauthapp/tinyauth >=0 <1.0.1-0.20260715123057-dade1e2c8f27 (fixed))
- Verified: https://github.com/advisories/GHSA-9xhm-w3wj-xhqh (GitHub-reviewed advisory GHSA-9xhm-w3wj-xhqh lists affected ranges: Go github.com/steveiliop56/tinyauth >=0 <1.0.1-0.20260715123057-dade1e2c8f27)

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