CVE-2025-66305: Grav vulnerable to Denial of Service via Improper Input Handling in 'Supported' Parameter

Severity: medium (CVSS 4.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2025-12-01 · updated 2026-06-17
Weakness: CWE-248

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.

Affected products

getgrav grav: from 1.7.48 before 1.8.0; 1.8.0-beta1, 1.8.0-beta10, 1.8.0-beta11, 1.8.0-beta12, 1.8.0-beta13, 1.8.0-beta14 (+20) — fixed in 1.8.0

How to fix

Upgrade to a fixed version: getgrav grav 1.8.0. Check the vendor advisory for mitigations.

References

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