GHSA-9p3p-w5jf-8xxg
Kirby vulnerable to path traversal in the router for PHP's built-in server
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
getkirby/cms🐘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 all Kirby setups that use PHP's built-in server. Such setups are commonly only used during local development.
Sites that use other server software (such as Apache, nginx or Caddy) are not affected.
Introduction
For use with PHP's built-in web server, Kirby provides a router.php file. The router delegates requests to static files to PHP so that assets and other static files in the document root can be accessed by the browser.
This logic was vulnerable against path traversal attacks. 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.
Impact
The missing path traversal check allowed attackers to navigate all files on the server that were accessible to the PHP process, including files outside of the Kirby installation.
The vulnerable implementation delegated all existing files to PHP, including existing files outside of the document root. This leads to a different response that allows attackers to determine whether the requested file exists.
Because Kirby's router only delegates such requests to PHP and does not load or execute them, contents of the files were not exposed as PHP treats requests to files outside of the document root as invalid.
Patches
The problem has been patched in Kirby 3.9.8.3, Kirby 3.10.1.2 and Kirby 4.7.1. Please update to one of these or a later version to fix the vulnerability.
In all of the mentioned releases, we have updated the router to check if existing static files are within the document root. Requests to files outside the document root are treated as page requests of the error page and will no longer allow to determine whether the file exists or not.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | getkirby/cms | all versions | 3.9.8.3 |
| 🐘Packagist | getkirby/cms | ≥ 3.10.0&&< 3.10.1.2 | 3.10.1.2 |
| 🐘Packagist | getkirby/cms | ≥ 4.0.0&&< 4.7.1 | 4.7.1 |
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 3.9.8.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9p3p-w5jf-8xxg 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-9p3p-w5jf-8xxg 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-9p3p-w5jf-8xxg. 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-9p3p-w5jf-8xxg in your dependencies?
O3 detects GHSA-9p3p-w5jf-8xxg across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.