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

> Attackers can enumerate valid usernames via timing differences, facilitating targeted credential attacks against Tinyauth authentication server.

- **Severity:** Medium 6.9 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Sep 2026
- **Updated:** 23 Sep 2026
- **Also known as:** GHSA-456h-ww26-f758, GO-2026-6555

## What is CVE-2026-77582?

CVE-2026-77582 is a medium-severity vulnerability in tinyauthapp tinyauth, published on 21 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-208 (Observable Timing Discrepancy)

## Which versions are affected by CVE-2026-77582?

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 | 1.0.1-0.20260714134959-c22925c2fba9 |
| `github.com/tinyauthapp/tinyauth` | Go | All versions | 1.0.1-0.20260714134959-c22925c2fba9 |
| `github.com/tinyauthapp/tinyauth` | Go | All versions | 1.0.1-0.20260714134959-c22925c2fba9 |

## How do I fix CVE-2026-77582?

Upgrade github.com/tinyauthapp/tinyauth to 1.0.1-0.20260714134959-c22925c2fba9 or later.

## Is CVE-2026-77582 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77582 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77582 and fix it if it is affected.

What it is: CVE-2026-77582 is a medium-severity vulnerability in tinyauthapp tinyauth, published on 21 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77582 exists.

Affected packages and fixed versions:
- github.com/tinyauthapp/tinyauth (Go): affected all versions; fixed in 1.0.1-0.20260714134959-c22925c2fba9
- github.com/tinyauthapp/tinyauth (Go): affected all versions; fixed in 1.0.1-0.20260714134959-c22925c2fba9
- github.com/tinyauthapp/tinyauth (Go): affected all versions; fixed in 1.0.1-0.20260714134959-c22925c2fba9

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-2026-77582/ (Markdown: https://insights.sbomify.com/CVE-2026-77582/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77582
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77582
- OSV: https://osv.dev/vulnerability/CVE-2026-77582

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77582/
Summaries are generated and may contain mistakes; the official description above is the record.