CVE-2025-66305 Grav vulnerable to Denial of Service via Improper Input Handling in 'Supported' Parameter
An attacker can cause a complete site outage by submitting malformed input to the Supported parameter in the Grav admin panel.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-66305?
CVE-2025-66305 is a medium-severity denial of service vulnerability in Getgrav Grav, published on 1 Dec 2025. An attacker needs administrator access to exploit it, with no action from the victim.
Official 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.
Weakness: CWE-248
Which versions are affected by CVE-2025-66305?
2 open source packages ship an affected version, including getgrav/grav. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
getgrav/grav Packagist | All versions | 1.8.0-beta.27 |
getgrav/grav Packagist | All versions | 1.8.0-beta.27 |
Products include Getgrav Grav.
How do I fix CVE-2025-66305?
Upgrade getgrav/grav to 1.8.0-beta.27 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-66305 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-66305 exists.
Other vulnerabilities in Getgrav Grav
- CVE-2023-34251 Grav Server Side Template Injection vulnerability
- CVE-2025-46199 Cross-site scripting in n/a
- CVE-2021-47812 GravCMS 1.10.7 - Arbitrary YAML Write/Update (Unauthenticated) (2)
- CVE-2025-66844 Grav may be vulnerable to SSRF attack via Twig Templates
- CVE-2022-2073 Code Injection in getgrav/grav
Sources
Also known as GHSA-m8vh-v6r6-w7p6.