Executive brief
Grav CMS, a popular content management system, contains multiple security flaws that could allow an attacker to take complete control of the server. These vulnerabilities stem from how the system handles internal data and administrative commands, potentially leading to unauthorized data access or full system compromise. Organizations using Grav should update to version 2.0.0-beta.2 or later to protect their operations and data.
Technical details
Grav CMS versions prior to 2.0.0-beta.2 contain five distinct RCE vectors. Three critical vulnerabilities involve unsafe PHP unserialize() calls in the JobQueue, FileCache, and Session components, where lack of class restriction allows for PHP object injection and gadget chain execution. An additional critical flaw in the InstallCommand component allows for OS command injection because branch, URL, and path parameters are passed to shell commands without proper escaping during git clone operations (requires admin privileges). Finally, a high-severity bypass in the Twig security blocklist allows for server-side template injection (SSTI). These issues are addressed in version 2.0.0-beta.2 through the implementation of HMAC-signed serialized envelopes, proper shell argument escaping, and an updated Twig sandbox.
Affected products
- Grav Grav CMS before 2.0.0-beta.2
Timeline
- 2026-04-24: patched: Fixes applied to the 2.0 branch by maintainers.
- 2026-04-27: advisory: GitHub Security Advisory published.
- 2026-06-30: disclosed: NVD publication and VulnCheck advisory.