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External Initialization of the Panel on .dev domains and some reverse proxy setups

Moderate
bastianallgeier published GHSA-2ccx-2gf3-8xvv Dec 2, 2020

Package

composer getkirby/panel, getkirby/cms (Composer)

Affected versions

<=2.5.13, 3.0.0-3.3.5

Patched versions

2.5.14, 3.3.6

Description

Impact

About our registration block

In order to protect new installations on public servers that don't have an admin account for the Panel yet, we block account registration there by default. This is a security feature, which we implemented years ago in Kirby 2. It helps to avoid that you forget registering your first admin account on a public server.

In this case – without our security block – someone else might theoretically be able to find your site, find out it's running on Kirby, find the Panel and then register the account first. It's an unlikely situation, but it's still a certain risk.

To be able to register the first Panel account on a public server, you have to enforce the installer via a config setting. This helps to push all users to the best practice of registering your first Panel account on your local machine and upload it together with the rest of the site.

The issue

As noted by Jukka Rautanen, this installation block implementation in Kirby versions before 3.3.6 still assumed that .dev domains are local domains, which is no longer true. In the meantime, those domains became publicly available. This means that our installation block is no longer working as expected if you use a .dev domain for your Kirby site.

In fixing this issue, we've also found out that the local installation check may also fail if your site is behind a reverse proxy.

Am I affected?

You are only affected if:

  1. you use a .dev domain or your site is behind a reverse proxy &
  2. you have not yet registered your first Panel account on the public server &
  3. someone finds your site and tries to login at yourdomain.dev/panel before you register your first account.

You are not affected if you have already created one or multiple Panel accounts (no matter if on a .dev domain or behind a reverse proxy).

Patches

The problem has been patched in Kirby 2.5.14 and Kirby 3.3.6. Please update to one of these or a later version to fix the vulnerability.

Note: Kirby 2 reaches end of life on December 31, 2020. We therefore recommend to upgrade your Kirby 2 sites to Kirby 3. If you cannot upgrade, we still recommend to update to Kirby 2.5.14.

Workarounds

Kirby 2 sites on older releases can also be patched by applying the changes from this commit.

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

CVE ID

CVE-2020-26253

Weaknesses