GHSA-JR9P-4H4J-6C58
Vulnerability from github – Published: 2026-07-14 00:07 – Updated: 2026-07-14 00:07Summary
The official Kimai Docker image ships with APP_SECRET=change_this_to_something_unique 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 APP_SECRET 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 super_admin.
Details
Dockerfile:263 sets ENV APP_SECRET=change_this_to_something_unique. This value is consumed by config/packages/framework.yaml:7 as kernel.secret, which Symfony uses to HMAC-sign:
- The
KIMAI_REMEMBERremember-me cookie - LoginLink signatures
- Password reset URLs
- CSRF tokens
The .docker/entrypoint.sh does not check for or replace the default sentinel value. The bare-metal .env.dist:38 ships the same default. No startup-time guard exists anywhere in the codebase that refuses to start when APP_SECRET equals the sentinel.
User IDs are sequential integers starting from 1. The first super_admin account is almost always id=1. User IDs are visible in some URLs and API responses.
A PoC was provided, but removed for security reasons.
Impact
Any Kimai instance deployed via the official Docker image without overriding APP_SECRET can be compromised from the internet. An unauthenticated attacker who can reach the Kimai URL can forge authentication tokens and log in as any user if:
- a username is known AND
- the correct account ID for this username is guessed AND
- the account has no active 2FA (two factor) authentication
Solution
- The entrypoint.sh file is updated and now contains a script that generates a random
APP_SECRETviabin2hex(random_bytes(32))which will be stored in/opt/kimai/var/data/.appsecret - The entrypoint.sh will create the file
/opt/kimai/.env.localcontaining theAPP_SECRET, either fetched from the Docker Environment or from the newly created secret file - The documentation was updated to highlight the importance of using a random secret for
APP_SECRET - The Dockerfile removed default
APP_SECRET=change_this_to_something_unique - Login links now contain more entropy (see GHSA-m492-gv72-xvxj) - so even without all previous changes, attackers won't be able to generate Login links even for installations that have a hard-coded
APP_SECRET=change_this_to_something_unique
See https://www.kimai.org/en/security/ghsa-jr9p-4h4j-6c58 for more information.
{
"affected": [
{
"database_specific": {
"last_known_affected_version_range": "\u003c= 2.57.0"
},
"package": {
"ecosystem": "Packagist",
"name": "kimai/kimai"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.58.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-52824"
],
"database_specific": {
"cwe_ids": [
"CWE-1188"
],
"github_reviewed": true,
"github_reviewed_at": "2026-07-14T00:07:59Z",
"nvd_published_at": null,
"severity": "CRITICAL"
},
"details": "### Summary\n\nThe official Kimai Docker image ships with `APP_SECRET=change_this_to_something_unique` 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 `APP_SECRET` 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 super_admin.\n\n### Details\n\n`Dockerfile:263` sets `ENV APP_SECRET=change_this_to_something_unique`. This value is consumed by `config/packages/framework.yaml:7` as `kernel.secret`, which Symfony uses to HMAC-sign:\n\n- The `KIMAI_REMEMBER` remember-me cookie\n- LoginLink signatures\n- Password reset URLs\n- CSRF tokens\n\nThe `.docker/entrypoint.sh` does not check for or replace the default sentinel value. The bare-metal `.env.dist:38` ships the same default. No startup-time guard exists anywhere in the codebase that refuses to start when `APP_SECRET` equals the sentinel.\n\nUser IDs are sequential integers starting from 1. The first super_admin account is almost always `id=1`. User IDs are visible in some URLs and API responses.\n\n*A PoC was provided, but removed for security reasons.*\n\n### Impact\n\nAny Kimai instance deployed via the official Docker image without overriding `APP_SECRET` can be compromised from the internet. An unauthenticated attacker who can reach the Kimai URL can forge authentication tokens and log in as any user if:\n- a username is known AND\n- the correct account ID for this username is guessed AND\n- the account has no active 2FA (two factor) authentication\n\n## Solution\n\n- The entrypoint.sh file is updated and now contains a script that generates a random `APP_SECRET` via `bin2hex(random_bytes(32))` which will be stored in `/opt/kimai/var/data/.appsecret`\n- The entrypoint.sh will create the file `/opt/kimai/.env.local` containing the `APP_SECRET`, either fetched from the Docker Environment or from the newly created secret file\n- The documentation was updated to highlight the importance of using a random secret for `APP_SECRET`\n- The Dockerfile removed default `APP_SECRET=change_this_to_something_unique`\n- Login links now contain more entropy (see GHSA-m492-gv72-xvxj) - so even without all previous changes, attackers won\u0027t be able to generate Login links even for installations that have a hard-coded `APP_SECRET=change_this_to_something_unique`\n\nSee [https://www.kimai.org/en/security/ghsa-jr9p-4h4j-6c58](https://www.kimai.org/en/security/ghsa-jr9p-4h4j-6c58) for more information.",
"id": "GHSA-jr9p-4h4j-6c58",
"modified": "2026-07-14T00:07:59Z",
"published": "2026-07-14T00:07:59Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/kimai/kimai/security/advisories/GHSA-jr9p-4h4j-6c58"
},
{
"type": "PACKAGE",
"url": "https://github.com/kimai/kimai"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Kimai: Default APP_SECRET in Docker Image Enables Cookie Forgery and Account Takeover"
}
Sightings
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