CVE-2026-75594

01/Description

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.

02/References7

• github.com/getkirby/kirby/commit/22fbaedb7e6dd61f5def10829ba7bd…
• github.com/getkirby/kirby/commit/a40808f5c2ee5d42bb597fb6ffbe0d…
• github.com/getkirby/kirby/commit/cd7abb68d298f3443eafd43fa2d0c7…
• github.com/getkirby/kirby/commit/e0dca5f709adc21b36f5549df2c061…
• github.com/getkirby/kirby/releases/tag/4.9.5
• github.com/getkirby/kirby/releases/tag/5.5.2
• github.com/getkirby/kirby/security/advisories/GHSA-9vx2-j98c-p7…