CVE-2026-75594: Getkirby Kirby

High severity, CVSS 8.2. EPSS: 0.8% chance of exploitation in the next 30 days.

Kirby is an open-source content management system. Prior to 4.9.5 and 5.5.2, depending on the release line, Kirby's media handler in src/Cms/Media.php allowed Kirby\Cms\Media::thumb() to append a path-bearing filename to a validated parent media directory. On nginx, PHP's built-in server, or Apache with AllowEncodedSlashes enabled, a remote attacker could submit encoded slash characters such as %2f in the filename and traverse outside the parent's media directory. Differences between responses for existing and nonexistent thumbnail configurations disclosed whether an arbitrary .json file existed, and a .json file containing a valid filename key could cause the referenced image to be returned and the job file to be deleted. The related file::version path in src/Filesystem/Asset.php also accepted ../ sequences outside the intended index root. This issue is fixed in versions 4.9.5 and 5.5.2.

Affected products

• Getkirby Kirby: before 4.9.5 (fixed in 4.9.5); from 5.0.0, before 5.5.2 (fixed in 5.5.2)

Published 2026-08-31. Last modified 2026-09-08.