Grav vulnerable to Denial of Service via Improper Input Handling in 'Supported' Parameter

Vulnerability Description

Grav is a file-based Web platform. Prior to 1.8.0-beta.27, a Denial of Service (DoS) vulnerability was identified in the "Languages" submenu of the Grav admin configuration panel (/admin/config/system). Specifically, the Supported parameter fails to properly validate user input. If a malformed value is inserted—such as a single forward slash (/) or an XSS test string—it causes a fatal regular expression parsing error on the server. This leads to application-wide failure due to the use of the preg_match() function with an improperly constructed regular expression, resulting in an error. Once triggered, the site becomes completely unavailable to all users. This vulnerability is fixed in 1.8.0-beta.27.

References

• https://github.com/getgrav/grav/security/advisories/GHSA-m8vh-v6r6-w7p6
• https://github.com/getgrav/grav/commit/ed640a13143c4177af013cf001969ed2c5e197ee