Pnetlab 5.3.11 Under Attack: Analyzing CVE-2025-63749 Command Injection Vulnerability

Overview

CVE-2025-63749 describes a critical command injection vulnerability found in Pnetlab version 5.3.11. This vulnerability allows an attacker to execute arbitrary commands on the system by manipulating the qemu_options parameter. This can lead to complete system compromise if exploited successfully.

Technical Details

The vulnerability resides within the handling of the qemu_options parameter in Pnetlab 5.3.11. Insufficient sanitization of user-supplied input in this parameter allows an attacker to inject arbitrary commands directly into the system’s command execution pipeline. This means a malicious actor could craft a request containing malicious code embedded within the qemu_options value. When Pnetlab processes this tainted value, it unknowingly executes the attacker’s injected commands. The exact mechanism and vulnerable code section requires further investigation, but the root cause is the lack of proper input validation and sanitization.

Specifically, the attack vector involves sending a specially crafted request to Pnetlab containing the malicious payload within the qemu_options parameter. The system then processes this request, leading to command execution.

CVSS Analysis

Currently, CVE-2025-63749 has a CVSS score of N/A. This likely indicates the score is still being calculated or that the vulnerability is being assessed. However, based on the description of command injection, it’s anticipated that this will receive a high to critical CVSS score due to the potential for complete system compromise. We will update this section as soon as the official CVSS score becomes available.

Factors contributing to a potentially high score include:

• Attack Vector: Likely Network (AV:N) if exploitable remotely.
• Attack Complexity: Potentially Low (AC:L) if the injection point is easily accessible.
• Privileges Required: Potentially None (PR:N) if no authentication is needed to reach the vulnerable function.
• User Interaction: Likely None (UI:N) as no user interaction is required to trigger the vulnerability.
• Scope: Changed (S:C) as successful exploitation could compromise the entire system, not just a single component.
• Confidentiality Impact: High (C:H) – Complete access to sensitive information.
• Integrity Impact: High (I:H) – Ability to modify system files and data.
• Availability Impact: High (A:H) – Ability to shut down or render the system unusable.

Possible Impact

The consequences of exploiting this vulnerability are severe. A successful attack could lead to:

• Complete system compromise: Attackers gain full control over the Pnetlab server.
• Data theft: Sensitive network configurations, user credentials, and other data can be exfiltrated.
• Malware installation: The compromised server can be used to host and distribute malware to other systems.
• Denial of service (DoS): The attacker can crash the server, rendering it unavailable.
• Lateral movement: A compromised Pnetlab server can be used as a stepping stone to attack other systems on the network.

Mitigation and Patch Steps

Currently, the best course of action is to:

• Upgrade Pnetlab: Upgrade to a patched version of Pnetlab as soon as one becomes available. The vendor should release a security patch to address this vulnerability. Check the official Pnetlab website for updates.
• Input Validation: If a patch isn’t immediately available, implement strict input validation and sanitization on the qemu_options parameter as a temporary workaround. This should involve filtering out any potentially malicious characters or commands. However, this is not a foolproof solution and should only be used as a temporary measure.
• Network Segmentation: Isolate the Pnetlab server on a segmented network to limit the potential damage from a successful attack.
• Web Application Firewall (WAF): Implement a Web Application Firewall (WAF) to detect and block malicious requests targeting the qemu_options parameter. Configure the WAF with rules to filter potentially harmful input.
• Monitor System Logs: Closely monitor system logs for suspicious activity, such as unusual command executions or unauthorized access attempts.

We strongly recommend upgrading Pnetlab to the latest version as soon as a patch is released to fully address this critical vulnerability.

References

GitHub Advisory – Pnetlab Command Injection (CVE-2025-63749)