Kimai: Username enumeration via timing on X-AUTH-USER

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Details src/API/Authentication/TokenAuthenticator.php calls loadUserByIdentifier() first and only invokes the password hasher (argon2id) when a user is returned. When the username does not exist, the request returns roughly 25 ms faster than when it does. The response body is the same in both cases ({"message":"Invalid credentials"}, HTTP 403), so the leak is purely timing. The /api/ firewall has no loginthrottling configured, so the probe is unbounded. The legacy X-AUTH-USER / X-AUTH-TOKEN headers are still accepted by default in 2.x. No prior authentication, no API token, and no session cookie are required. Proof of concept Usage: In this run, four real accounts were identified out of thirteen candidates with no false positives or false negatives. Probing took roughly five seconds per username at fifteen samples each. Fix In TokenAuthenticator::authenticate(), run the password hasher against a fixed dummy hash when the user is not found, so the response time does not depend on user…

Published by the source

17 Apr 2026, 22:30 UTC

Last modified by the source

17 Apr 2026, 22:31 UTC

Source last checked

26 Oct 2026, 14:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-jrc6-fmhw-fpq2

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# Patch Next advisory brief: GHSA-jrc6-fmhw-fpq2

Advisory: Kimai: Username enumeration via timing on X-AUTH-USER
IDs: GHSA-jrc6-fmhw-fpq2
Record: https://patchnext.com/advisories/ghsa-jrc6-fmhw-fpq2 (revision 1, source checked 26 Oct 2026, 14:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: kimai/kimai 2.54.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist kimai/kimai: affected <= 2.53.0; fixed in 2.54.0

## Suggested inspection (read-only)
- Packagist kimai/kimai: 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 kimai/kimai.
- 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://github.com/advisories/GHSA-jrc6-fmhw-fpq2 (GitHub-reviewed advisory GHSA-jrc6-fmhw-fpq2 lists affected ranges: Packagist kimai/kimai >=0 <=2.53.0)

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