Executive brief
Craft CMS is a popular content management system used to build and manage websites. A vulnerability in versions 4.8.0–4.18.5 and 5.0.0–5.10.12 allows any authenticated user without administrator privileges to execute arbitrary operating-system commands on the web server by exploiting confusion between two different signing mechanisms. An attacker with a regular user account can craft a malicious request that tricks the system into treating user-controlled cookie data as a legitimate redirect instruction, leading to code execution with the privileges of the web server.
Technical details
The vulnerability is a signature-key reuse flaw: Craft CMS uses the same HMAC key (securityKey) to sign both authentication cookies and redirect parameters, but does not bind the signature to its intended purpose. An authenticated user can set an attacker-controlled cookie via the license-shun endpoint; the signed cookie envelope can then be transplanted into a redirect parameter. On login, Craft validates the signature and passes the authenticated bytes to an unsandboxed Twig template engine. Twig's map filter accepts string callbacks in non-sandbox mode and allows invocation of PHP's system() function, enabling arbitrary command execution as the web-server user. Exploitation requires a regular account with password authentication, no 2FA, default configuration, and availability of PHP system() function. The issue is fixed in versions 4.18.6 and 5.10.13.
Affected products
- Craft CMS 4.8.0 through 4.18.5, 5.0.0 through 5.10.12
Timeline
- 2026-09-01: disclosed: GitHub Security Advisory published
- 2026-09-16: advisory: NVD and CVE-2026-92592 published
- 2026-09-16: patched: Fixed in versions 4.18.6 and 5.10.13