Tinyauth: User enumeration attack by timing oracle

Exploitation

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

CVSS 4.0

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 · score source

EPSS

• CVE-2026-77582: 0.63% estimated exploitation activity in the next 30 days; percentile 50.05 (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 It's possible to enumerate users through a timing oracle. In other words: I can easily check if a username exists or not by observing the timing differences between logins. PoC Setup a tinyauth server with a local user. It can be over the network. Try to log in with the local user, using an incorrect password: there is a noticeable delay. You know that the user exists. Now try to log in with a username that does not exist, using an incorrect password: it will complete almost immediately. You know that the user does not exist. Expected vs actual behavior Login attempts should take roughly the same amount of time when the user exists vs when the user does not exist. Right now, nonexistent user attempts are way faster, meaning if your login attempt is slow, then the username exists for sure. Details Existing usernames will take an extra ~50 milliseconds to respond to login attempts, while non-existing usernames will take only ~50 microseconds (1000x less time) to return an…

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 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-456h-ww26-f758

2. Revision 3 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6555

4. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-456h-ww26-f758

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# Patch Next advisory brief: CVE-2026-77582

Advisory: Tinyauth: User enumeration attack by timing oracle
IDs: CVE-2026-77582, GHSA-456h-ww26-f758
Record: https://patchnext.com/advisories/cve-2026-77582 (revision 4, 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 6.9)
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 1.0.1-0.20260714134959-c22925c2fba9. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/tinyauthapp/tinyauth: affected < 1.0.1-0.20260714134959-c22925c2fba9; fixed in 1.0.1-0.20260714134959-c22925c2fba9

## Suggested inspection (read-only)
- Go github.com/tinyauthapp/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.
- 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-456h-ww26-f758 (OSV record GHSA-456h-ww26-f758 lists affected ranges: Go github.com/tinyauthapp/tinyauth >=0 <1.0.1-0.20260714134959-c22925c2fba9 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6555 (OSV record GO-2026-6555 lists affected ranges: Go github.com/tinyauthapp/tinyauth >=0 <1.0.1-0.20260714134959-c22925c2fba9 (fixed))
- Verified: https://github.com/advisories/GHSA-456h-ww26-f758 (GitHub-reviewed advisory GHSA-456h-ww26-f758 lists affected ranges: Go github.com/tinyauthapp/tinyauth >=0 <1.0.1-0.20260714134959-c22925c2fba9)

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