---
id: "CVE-2026-77582"
kind: "vulnerability"
aliases: ["CVE-2026-77582", "GHSA-456h-ww26-f758", "GO-2026-6555"]
title: "Tinyauth: User enumeration attack by timing oracle in github.com/tinyauthapp/tinyauth"
severity: "medium"
cvss: 6.9
epss: 0.00481
exploited: false
status: "open"
category: "package"
products: [{"name": "github.com/tinyauthapp/tinyauth", "fixed": ["1.0.1-0.20260714134959-c22925c2fba9"], "affected": "< 1.0.1-0.20260714134959-c22925c2fba9", "ecosystem": "go"}]
ecosystems: ["go"]
tags: ["go", "package", "self-hosted", "tinyauth"]
not_affected_if: []
published_at: "2026-09-21T17:18:53+00:00"
first_seen_at: "2026-10-23T19:13:08+00:00"
updated_at: "2026-10-23T21:46:00+00:00"
sources: [{"source": "govuln", "url": "https://pkg.go.dev/vuln/GO-2026-6555", "first_seen_at": "2026-10-23T19:13:08+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-77582", "first_seen_at": "2026-10-23T19:13:43+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-77582", "first_seen_at": "2026-10-23T19:35:23+00:00"}]
---

# Tinyauth: User enumeration attack by timing oracle in github.com/tinyauthapp/tinyauth

Tinyauth's login and basic-auth paths respond measurably faster for nonexistent usernames than for existing ones, because bcrypt password checking only runs for real accounts. A remote attacker can time repeated login attempts to discover valid usernames and then target them with password guessing.

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

## Affected

- go:github.com/tinyauthapp/tinyauth affected < 1.0.1-0.20260714134959-c22925c2fba9 fixed 1.0.1-0.20260714134959-c22925c2fba9

## How to check

Check the tinyauth version in go.mod: go list -m github.com/tinyauthapp/tinyauth
Affected if older than 1.0.1-0.20260714134959-c22925c2fba9 (govuln) or older than 5.1.0 (description).

## Fix

Upgrade github.com/tinyauthapp/tinyauth to 1.0.1-0.20260714134959-c22925c2fba9 (govuln) or 5.1.0 (description); the sources disagree on the fixed version.

## Timeline

- 2026-10-23T19:13:08+00:00 govuln https://pkg.go.dev/vuln/GO-2026-6555
- 2026-10-23T19:13:43+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-77582
- 2026-10-23T19:35:23+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-77582

## From the sources

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.

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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_