CVE-2026-44177 — getkirby / cms
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')TL;DR
This vulnerability affects all Kirby sites on Kirby 5.3.0-5.4.0 and is independent from setup conditions and authentication.
This vulnerability is of high severity for all Kirby sites.
Introduction
Path traversal is a type of attack that allows to access arbitrary filesystem paths. By using special elements such as .. and / separators, attackers can escape outside of the restricted location to access files or directories that are elsewhere on the system. One of the most common special elements is the ../ sequence, which in most modern operating systems is interpreted as the parent directory of the current location. Path traversal can give attackers information about the filesystem and directory structure on the server and can lead to additional attacks depending on the nature of the accessible files and directories.
PHP file inclusion is a type of attack that allows to load and execute PHP files on the server that are not intended for direct inclusion. Depending on the logic inside the PHP files, this can lead to disclosure of sensitive information or unintended, malicious actions.
Affected components
Kirby's Users collection received a performance improvement in Kirby 5.3.0. Starting in this release, Kirby loads user objects lazily when they are first needed. Users are queried by their user ID, which is then used to look up the user's account directory in the site/accounts directory.
This applies to the authentication API (accessible to unauthenticated requests), the users API (accessible to authenticated users only) as well as to other places that use $users->find() to look up an individual user with a request-provided email or user ID.
Impact
In affected releases, Kirby did not correctly validate the provided user ID, causing a path traversal vulnerability. This vulnerability results in the following impact:
- Arbitrary PHP file inclusion of files with the filename
index.php(e.g. the main PHP files of plugins), the impact of which depends on the contents and logic inside the includable files. - Probing of the existence of arbitrary directories on the server, which can allow attackers to fingerprint the server and site setup, including installed plugins and the content structure.
Patches
The problem has been patched in Kirby 5.4.1. Please update to this or a later version to fix the vulnerability.
In the mentioned release, Kirby has added additional checks to the user lookup that ensure that the provided user ID only contains valid characters and that the resulting path to the account directory is contained in the site/accounts directory.
Credits
Kirby thanks @offset for responsibly reporting the identified issue.
| Software | From | Fixed in |
|---|---|---|
getkirby / cms
|
5.3.0 | 5.4.1 |
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Frequently Asked Questions
A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.
Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.
Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
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