Overview
CVE-2025-65221 details a buffer overflow vulnerability found in the Tenda AC21 router, specifically version V16.03.08.16. This vulnerability exists in the /goform/setPptpUserList endpoint and is triggered via the list parameter. Exploitation of this vulnerability could potentially allow an attacker to execute arbitrary code on the device, leading to a compromise of the router and the network it serves.
Technical Details
The vulnerability is located within the /goform/setPptpUserList endpoint of the Tenda AC21’s web interface. The list parameter, which is likely intended to handle a list of PPTP user configurations, is not properly validated for length. Sending an overly long string as the value of the list parameter causes a buffer overflow, overwriting adjacent memory regions. This can potentially allow an attacker to inject and execute malicious code. The specific mechanism used to exploit the overflow would depend on the architecture and memory layout of the Tenda AC21 router.
The vulnerability details were published on GitHub in the following repository: MY_VULN_2/blob/main/Tenda/VULN2.md
CVSS Analysis
Currently, a CVSS score and severity rating have not been assigned to CVE-2025-65221. This may be due to the vulnerability being newly discovered or not yet analyzed by security researchers or vulnerability scoring organizations. However, given that it’s a buffer overflow, it’s highly likely to be assigned a HIGH severity score once analyzed.
We expect a formal CVSS score to be published on resources like the NIST National Vulnerability Database (NVD) and the FIRST CVSS website soon.
Possible Impact
A successful exploit of this buffer overflow vulnerability could have significant consequences, including:
- Remote Code Execution (RCE): An attacker could potentially execute arbitrary code on the router, gaining complete control of the device.
- Router Compromise: The router could be turned into a botnet node, used for malicious activities like DDoS attacks or spam distribution.
- Network Interception: An attacker could intercept network traffic, potentially stealing sensitive information like usernames, passwords, and financial data.
- Denial of Service (DoS): The router could be rendered unusable, disrupting internet access for all connected devices.
- Lateral Movement: An attacker could use the compromised router as a pivot point to access other devices on the network.
Mitigation and Patch Steps
To mitigate the risk associated with CVE-2025-65221, the following steps are recommended:
- Firmware Update: Check the Tenda website (Tenda Website) for a firmware update that addresses this vulnerability. Apply the update as soon as it becomes available.
- Disable Remote Management: If possible, disable remote management access to the router’s web interface. This reduces the attack surface.
- Strong Passwords: Ensure that the router’s administrative password is strong and unique.
- Network Segmentation: Implement network segmentation to limit the potential impact of a compromised router on other devices.
- Monitor Network Traffic: Monitor network traffic for suspicious activity, such as unusual outbound connections.
Contact Tenda support directly for assistance in securing your device.
References
- GitHub Advisory: MY_VULN_2/blob/main/Tenda/VULN2.md
- Tenda Official Website: https://www.tenda.com.cn/
- NIST National Vulnerability Database (NVD): https://nvd.nist.gov/
- FIRST CVSS: https://www.first.org/cvss/
