CVE-2026-52824: Kimai: Default APP_SECRET in Docker Image Enables Cookie Forgery and Account Takeover

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 1.3%, percentile 71: FIRST’s model estimates a 1.3% chance of exploitation activity in the next 30 days, higher than 71% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes kimai/kimai (Composer (PHP)) <= 2.57.0, fixed in 2.58.0. Check your lockfile, including transitive dependencies.

What it is

Kimai is an open-source time tracking application. Prior to 2.58.0, the official Docker image sets APPSECRET to the public value changethistosomethingunique in Dockerfile, and .docker/entrypoint.sh neither replaces nor rejects that value before Symfony uses it as kernel.secret. An unauthenticated attacker who reaches a deployment that did not override APPSECRET, knows a username, correctly guesses the account ID associated with that username, and targets an account without active two-factor authentication can forge HMAC-protected authentication artifacts, including KIMAIREMEMBER cookies and login links, to access the account without its password. The updated entrypoint generates and persists a random secret when no safe operator-provided value exists. This issue is fixed in version 2.58.0.

From the GitHub advisory

Summary

The official Kimai Docker image ships with APPSECRET=changethistosomethingunique as the default environment variable. The Docker entrypoint does not override or validate this value. Any Kimai instance deployed using the Docker image without explicitly setting APPSECRET runs with a publicly-known Symfony kernel.secret, enabling an unauthenticated attacker to forge HMAC-signed cookies and login links to take over any account including superadmin.

Details

Dockerfile:263 sets ENV APPSECRET=changethistosomethingunique. This value is consumed by config/packages/framework.yaml:7 as kernel.secret, which Symfony uses to HMAC-sign:

- The KIMAIREMEMBER remember-me cookie - LoginLink signatures - Password reset URLs - CSRF tokens

Weakness type: CWE-1188.

Product: kimai/kimai (Composer (PHP)) · Assigned by: GitHub_M · Published: 2026-09-15

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: high (needs special conditions)
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 1.33% probability of exploitation activity in the next 30 days; percentile 71.

Timeline

• 2026-07-14 — GitHub-reviewed advisory GHSA-jr9p-4h4j-6c58 published (critical)
• 2026-09-15 — CVE record published by GitHub_M
• 2026-09-16 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-jr9p-4h4j-6c58 github.com
2. CVE.org record CVE-2026-52824 cve.org
3. NVD entry CVE-2026-52824 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. kimai.org kimai.org

Critical Composer (PHP) advisories · Today’s Security Digest