EUVD-2025-5950

Comprehensive Technical Analysis of EUVD-2025-5950

1. Vulnerability Assessment and Severity Evaluation

The vulnerability described in EUVD-2025-5950 affects multiple models of Draytek Vigor routers. The issue lies in the CGI endpoint used for uploading configurations, which allows attackers to upload a crafted kernel module, leading to arbitrary code execution. The CVSS (Common Vulnerability Scoring System) base score of 9.8 indicates a critical severity level. The scoring vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H breaks down as follows:

• Attack Vector (AV): Network (N) - The vulnerability is exploitable over the network.
• Attack Complexity (AC): Low (L) - The attack requires minimal complexity.
• Privileges Required (PR): None (N) - No privileges are required to exploit the vulnerability.
• User Interaction (UI): None (N) - No user interaction is required.
• Scope (S): Unchanged (U) - The vulnerability does not change the security scope.
• Confidentiality (C): High (H) - The vulnerability has a high impact on confidentiality.
• Integrity (I): High (H) - The vulnerability has a high impact on integrity.
• Availability (A): High (H) - The vulnerability has a high impact on availability.

2. Potential Attack Vectors and Exploitation Methods

The primary attack vector is through the CGI endpoint used for configuration uploads. An attacker can exploit this vulnerability by:

• Network Access: Gaining network access to the affected Draytek devices.
• Crafted Kernel Module: Uploading a specially crafted kernel module through the vulnerable CGI endpoint.
• Arbitrary Code Execution: Executing arbitrary code on the device, which can lead to full control over the router.

Potential exploitation methods include:

• Remote Code Execution (RCE): By uploading a malicious kernel module, attackers can execute arbitrary code on the device.
• Privilege Escalation: Once code execution is achieved, attackers can escalate privileges to gain full control over the router.
• Data Exfiltration: Attackers can exfiltrate sensitive data, including configuration files and network traffic.

3. Affected Systems and Software Versions

The vulnerability affects the following Draytek Vigor models and software versions:

• Vigor 165/166 prior to v4.2.6
• Vigor 2620/LTE200 prior to v3.9.8.8
• Vigor 2860/2925 prior to v3.9.7
• Vigor 2862/2926 prior to v3.9.9.4
• Vigor 2133/2762/2832 prior to v3.9.8
• Vigor 2135/2765/2766 prior to v4.4.5.1
• Vigor 2865/2866/2927 prior to v4.4.5.3
• Vigor 2962/3910 prior to v4.3.2.7
• Vigor 3912 prior to v4.3.5.2
• Vigor 2925 up to v3.9.6

4. Recommended Mitigation Strategies

To mitigate the risk associated with this vulnerability, the following strategies are recommended:

• Update Firmware: Immediately update the firmware of affected Draytek devices to the latest versions that address this vulnerability.
• Network Segmentation: Implement network segmentation to isolate critical systems and reduce the attack surface.
• Access Control: Enforce strict access controls and limit network access to the affected devices.
• Monitoring and Logging: Implement robust monitoring and logging mechanisms to detect and respond to suspicious activities.
• Intrusion Detection Systems (IDS): Deploy IDS to identify and alert on potential exploitation attempts.
• Regular Audits: Conduct regular security audits and vulnerability assessments to identify and address potential security gaps.

5. Impact on European Cybersecurity Landscape

The vulnerability poses a significant risk to the European cybersecurity landscape, particularly for organizations and individuals using Draytek Vigor routers. The potential for arbitrary code execution and data exfiltration can lead to:

• Compromised Network Security: Attackers can gain unauthorized access to networks, leading to data breaches and loss of sensitive information.
• Service Disruption: Attackers can disrupt network services, affecting business operations and critical infrastructure.
• Compliance Issues: Organizations may face compliance issues and regulatory penalties if sensitive data is compromised.

6. Technical Details for Security Professionals

For security professionals, the following technical details are crucial:

• Vulnerability Identification: The vulnerability is identified as CVE-2024-41339 and GHSA-cpr3-4f88-q3jq.
• Exploitation Steps:
  1. Identify the vulnerable Draytek device and its firmware version.
  2. Gain network access to the device.
  3. Craft a malicious kernel module.
  4. Upload the crafted module through the vulnerable CGI endpoint.
  5. Execute arbitrary code on the device.
• Detection Methods:
  • Monitor network traffic for unusual activities, particularly around the CGI endpoint.
  • Implement anomaly detection to identify deviations from normal behavior.
  • Use signature-based detection to identify known exploitation patterns.
• Response Actions:
  • Isolate the affected device from the network.
  • Update the firmware to the latest version.
  • Conduct a thorough security audit to identify and mitigate any additional vulnerabilities.

By understanding the technical details and implementing the recommended mitigation strategies, security professionals can effectively protect against this critical vulnerability and maintain the integrity and security of their networks.