EUVD-2026-9197

Comprehensive Technical Analysis of EUVD-2026-9197

1. Vulnerability Assessment and Severity Evaluation

Vulnerability Description: The vulnerability in Tenda W20E V4.0br_V15.11.0.6 arises from a lack of size validation for the addDhcpRules data, which can lead to buffer overflows in the dhcpsIndex, dhcpsIP, and dhcpsMac variables. This issue occurs when the sscanf function processes overly long input data without proper bounds checking.

Severity Evaluation: The Base Score of 9.8 (CVSS:3.1) indicates a critical vulnerability. The scoring vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H highlights the following:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): None (N)
• Scope (S): Unchanged (U)
• Confidentiality (C): High (H)
• Integrity (I): High (H)
• Availability (A): High (H)

This high score underscores the potential for severe impact on confidentiality, integrity, and availability of the affected system.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• Network-based Attacks: Given the network attack vector, an attacker can exploit this vulnerability remotely without needing physical access to the device.
• Malicious Input: Attackers can send specially crafted addDhcpRules data to trigger the buffer overflow.

Exploitation Methods:

• Buffer Overflow: By sending overly long data, an attacker can overwrite adjacent memory, potentially leading to arbitrary code execution or denial of service.
• Remote Code Execution (RCE): If the buffer overflow allows for code injection, an attacker could execute arbitrary code on the device.

3. Affected Systems and Software Versions

Affected Systems:

• Tenda W20E V4.0br_V15.11.0.6

Software Versions:

• Firmware version V15.11.0.6

4. Recommended Mitigation Strategies

Immediate Mitigation:

• Network Segmentation: Isolate the affected devices from critical networks to limit the potential impact of an attack.
• Firewall Rules: Implement strict firewall rules to block unauthorized access to the device.
• Monitoring: Increase monitoring of network traffic to detect any unusual activity.

Long-term Mitigation:

• Firmware Update: Apply the latest firmware updates from Tenda as soon as they are available.
• Input Validation: Ensure that all input data is properly validated and sanitized before processing.
• Security Audits: Conduct regular security audits and vulnerability assessments to identify and mitigate similar issues.

5. Impact on European Cybersecurity Landscape

Regulatory Compliance:

• GDPR: Organizations must ensure that personal data is protected, and a breach due to this vulnerability could result in significant fines.
• NIS Directive: Critical infrastructure providers must comply with the Network and Information Systems Directive, which mandates robust cybersecurity measures.

Economic Impact:

• Business Disruption: A successful exploit could lead to service disruptions, impacting business operations and customer trust.
• Financial Losses: Potential data breaches could result in financial losses due to legal penalties and remediation costs.

Reputation:

• Brand Damage: Organizations affected by this vulnerability may suffer reputational damage, impacting customer loyalty and market position.

6. Technical Details for Security Professionals

Vulnerability Details:

• Function Affected: addDhcpRule
• Code Snippet: ret = sscanf(pRule, " %d\t%[^\t]\t%[^\n\r\t]", &dhcpsIndex, dhcpsIP, dhcpsMac);
• Issue: Lack of size validation for dhcpsIndex, dhcpsIP, and dhcpsMac.

Exploitation:

• Payload Crafting: Attackers can craft payloads with overly long data to trigger the buffer overflow.
• Memory Corruption: The overflow can corrupt memory, leading to arbitrary code execution or crashes.

Detection:

• Intrusion Detection Systems (IDS): Implement IDS to detect unusual network traffic patterns indicative of exploitation attempts.
• Log Analysis: Regularly analyze logs for anomalies that may indicate an attack.

Remediation:

• Code Review: Conduct a thorough code review to identify and fix similar vulnerabilities.
• Secure Coding Practices: Adopt secure coding practices to prevent buffer overflows and other common vulnerabilities.

References:

• Tenda Security Advisory
• GitHub CVE Report

By addressing this vulnerability promptly and comprehensively, organizations can mitigate the risk of exploitation and ensure the security and integrity of their systems.