Summary
Kirby CMS has pre-authentication path traversal and PHP file inclusion during user lookup
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.
Credits
Kirby thanks @offset for responsibly reporting the identified issue.
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.
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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.
Frequently Asked Questions
- What is CVE-2026-44177? CVE-2026-44177 is a high-severity path traversal vulnerability in getkirby/cms (composer), affecting versions >= 5.3.0, <= 5.4.0. It is fixed in 5.4.1. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- Which versions of getkirby/cms are affected by CVE-2026-44177? getkirby/cms (composer) versions >= 5.3.0, <= 5.4.0 is affected.
- Is there a fix for CVE-2026-44177? Yes. CVE-2026-44177 is fixed in 5.4.1. Upgrade to this version or later.
- Is CVE-2026-44177 exploitable, and should I be worried? Whether CVE-2026-44177 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-44177 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-44177? Upgrade
getkirby/cmsto 5.4.1 or later.