---
id: CVE-2026-80199
title: >-
  Kimai before 2.54.0 contains a timing oracle vulnerability in
  TokenAuthenticator that allows unauthenticated attackers to enumerate valid
  usernames via X-AUTH-USER header
summary: >-
  Kimai before 2.54.0 contains a timing oracle vulnerability in
  TokenAuthenticator that allows unauthenticated attackers to enumerate valid
  usernames via X-AUTH-USER header. Attackers can measure response time
  differences when the password…
severity: low
cvss: 3.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N'
cwe:
  - CWE-208
vendor: kimai
product: kimai
affected:
  - kimai < 2.54.0
published: '2026-08-26'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T16:17:45.830'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-80199'
references:
  - url: 'https://github.com/kimai/kimai/security/advisories/GHSA-jrc6-fmhw-fpq2'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/kimai-before-2.54.0-username-enumeration-via-timing-oracle
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-08-26T12:07:02.895233Z'
epss: 0.00308
epssPercentile: 0.21688
ingestedAt: '2026-10-08T16:52:14.730Z'
---

## Overview

Kimai before 2.54.0 contains a timing oracle vulnerability in TokenAuthenticator that allows unauthenticated attackers to enumerate valid usernames via X-AUTH-USER header. Attackers can measure response time differences when the password hasher runs only for existing users, enabling username enumeration with no login throttling protection.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.