CVE-2026-30461: Daylight Studio FuelCMS RCE Vulnerability

CVE-2026-30461 Overview

Daylight Studio FuelCMS v1.5.2 contains an authenticated remote code execution (RCE) vulnerability in the /controllers/Installer.php file, specifically within the add_git_submodule function. This command injection vulnerability (CWE-77) allows authenticated attackers to execute arbitrary commands on the underlying server by exploiting improper input sanitization in the Git submodule functionality.

Critical Impact

Authenticated attackers can achieve full server compromise through arbitrary command execution, potentially leading to data exfiltration, lateral movement, and complete system takeover.

Affected Products

• Daylight Studio FuelCMS v1.5.2
• FuelCMS installations using the vulnerable Installer.php controller
• Systems with Git submodule functionality enabled

Discovery Timeline

• 2026-04-15 - CVE CVE-2026-30461 published to NVD
• 2026-04-16 - Last updated in NVD database

Technical Details for CVE-2026-30461

Vulnerability Analysis

This vulnerability is classified as CWE-77 (Command Injection), where user-supplied input is improperly passed to system commands without adequate sanitization. The add_git_submodule function within the Installer controller fails to properly validate or escape parameters before executing Git commands on the server.

The vulnerability requires authentication to exploit, meaning an attacker must first obtain valid credentials to access the administrative interface. However, once authenticated, the attacker can leverage this flaw to execute arbitrary commands with the privileges of the web server process, typically leading to complete server compromise.

The network-accessible nature of this vulnerability combined with low attack complexity makes it particularly dangerous for internet-exposed FuelCMS installations.

Root Cause

The root cause lies in the add_git_submodule function within /controllers/Installer.php. The function constructs shell commands using user-supplied input without proper sanitization or escaping. This allows an authenticated attacker to inject additional shell commands through specially crafted input parameters that are passed directly to the system command execution functions.

Attack Vector

The attack vector is network-based and requires low-privilege authentication. An attacker with valid credentials can access the Installer controller and invoke the add_git_submodule functionality with malicious input. By injecting shell metacharacters or command separators into the Git submodule parameters, the attacker can break out of the intended command context and execute arbitrary system commands.

The exploitation flow typically involves:

1. Authenticating to the FuelCMS administrative interface
2. Accessing the Installer controller endpoints
3. Crafting a malicious request to the add_git_submodule function with injected commands
4. The server executes the injected commands with web server privileges

For detailed technical analysis of this vulnerability, refer to the Pentest Tools RCE Analysis and the GitHub FUEL CMS Installer source code.

Detection Methods for CVE-2026-30461

Indicators of Compromise

• Unusual HTTP requests to /fuel/modules/fuel/controllers/Installer.php endpoints
• Server access logs showing suspicious parameters containing shell metacharacters (;, |, $(), backticks)
• Unexpected processes spawned by the web server user account
• Anomalous network connections originating from the web server process
• Evidence of command execution artifacts in web server error logs

Detection Strategies

• Implement Web Application Firewall (WAF) rules to detect command injection patterns in requests to FuelCMS Installer endpoints
• Monitor web server logs for requests to the Installer controller containing shell metacharacters or command separators
• Deploy endpoint detection and response (EDR) solutions to identify suspicious child processes spawned by web server processes
• Utilize SentinelOne Singularity to detect behavioral indicators of post-exploitation activity following command injection

Monitoring Recommendations

• Enable verbose logging for the FuelCMS application and monitor for requests to the Installer controller
• Configure SIEM alerts for patterns matching command injection attempts in HTTP request parameters
• Monitor system process trees for unexpected command execution originating from PHP or web server processes
• Implement file integrity monitoring on critical FuelCMS directories to detect unauthorized modifications

How to Mitigate CVE-2026-30461

Immediate Actions Required

• Restrict access to the Installer controller to trusted IP addresses only using firewall rules or web server configuration
• Disable or remove the add_git_submodule functionality if not actively required
• Review and audit user accounts with administrative access to FuelCMS
• Implement additional authentication controls such as multi-factor authentication for administrative access
• Consider temporarily taking vulnerable FuelCMS installations offline until a patch is available

Patch Information

At the time of publication, no official patch has been released by Daylight Studio for this vulnerability. Administrators should monitor the Fuel CMS Home Page and Daylight Home Page for security updates. The vulnerable code can be reviewed at the GitHub FUEL CMS Installer repository.

Workarounds

• Apply web server configuration to block requests to the Installer controller endpoints entirely
• Implement input validation at the web server level using ModSecurity or similar WAF with rules to reject requests containing shell metacharacters
• Use network segmentation to isolate FuelCMS servers from sensitive internal resources
• Restrict the web server user's system privileges using mandatory access controls like SELinux or AppArmor

# Apache configuration to restrict Installer controller access
<LocationMatch "/fuel/modules/fuel/controllers/Installer\.php">
    Require ip 10.0.0.0/8 192.168.0.0/16
    # Alternatively, deny all access:
    # Require all denied
</LocationMatch>