GHSA-whxw-24jc-cwmv
Kirby: External Initialization of the Panel on reverse proxy setups with the `Forwarded` header
Blast Radius
getkirby/cms🐘getkirby/cmsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
TL;DR
This vulnerability affects Kirby sites that have no configured user accounts and are running on publicly accessible servers behind a reverse proxy that sets the Forwarded: for=..., X-Client-IP, or X-Real-IP request header.
It was possible to install the Panel (= create the first admin user) in these setups even from remote IP addresses.
This vulnerability is of critical severity for affected sites.
Your site is not affected if any of the following apply:
- An admin account has already been configured
- The Panel and API are disabled
- The site is not running behind a reverse proxy
- The reverse proxy sets the
X-Forwarded-FororClient-IPheader instead of the affected ones.
Introduction
External Initialization is a type of vulnerability that allows attackers to initialize a system or configuration value without authentication.
This can give untrusted actors access to the system or let them control its behavior.
Affected components
The Kirby Panel and REST API are authenticated by local user accounts. If a Kirby installation does not yet have any users, it first needs to be installed. During the installation process, an initial admin user account is created.
To protect against external initialization attacks that would allow untrusted actors to create an admin user for the Kirby installation, Kirby already checked whether the current request came from a local IP address. This allows installing the Panel in local development setups. Installation on remote servers was only supposed to be possible when the panel.install configuration option was enabled.
The isLocal check takes all relevant request headers into account and treats a request as non-local as soon as any checked request header contains an external IP address.
Impact
In affected releases, the isLocal check for the installation logic did not properly take the Forwarded: for=... header into account. This header is set by modern reverse proxy servers. It also did not take into account the X-Client-IP or X-Real-IP headers, which are set by some custom reverse proxy setups.
This caused Kirby to falsely assume that an installation request was local and allowed creating an admin account even though the reverse proxy forwarded the request from an external IP address.
Reverse proxies setting the X-Forwarded-For or Client-IP headers were not affected. These headers were already properly checked for external IP addresses.
Patches
The problem has been patched in Kirby 4.9.4 and Kirby 5.4.4. Please update to one of these or a later version to fix the vulnerability.
In all of the mentioned releases, we fixed the isLocal check to also properly take Forwarded: for=..., X-Client-IP and X-Real-IP request headers into account.
Workarounds
Sites on older Kirby versions (Kirby 3 starting at 3.7.0) can be protected with one of the following workarounds:
- Perform the Panel installation yourself by creating an initial admin account. As soon as one or more accounts are present, the vulnerable installation code is no longer active.
- If you don't need the Panel, disable the REST API with the
'api' => falseoption inconfig.php.
Credits
Thanks to Peter Levashov (@petersevera) for responsibly reporting the identified issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | getkirby/cms | all versions | 4.9.4 |
| 🐘Packagist | getkirby/cms | ≥ 5.0.0-alpha.1&&< 5.4.4 | 5.4.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for getkirby/cms. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update getkirby/cms to 4.9.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-whxw-24jc-cwmv is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-whxw-24jc-cwmv is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-whxw-24jc-cwmv. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-whxw-24jc-cwmv in your dependencies?
O3 detects GHSA-whxw-24jc-cwmv across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.