Introduction:

In the Tenda AC23 router, firmware version 16.03.07.45_cn, a critical security vulnerability has been discovered in the "sub_4781A4" function. This function does not properly validate user input, resulting in a post-authentication stack overflow vulnerability. Stack overflow vulnerabilities can allow attackers to execute arbitrary code on the target device, potentially leading to further compromise, intrusion, and impact on internal target systems.

In this post, we will dive into the exploit details, providing code snippets and referencing original sources to assist in understanding and mitigating this vulnerability.

Exploit Details

The vulnerability lies in the "sub_4781A4" function, which interacts with the web interface of the Tenda AC23 router. When an authenticated user enters data via this interface, the "sub_4781A4" function does not properly validate the entered data, potentially causing a buffer overflow on the router's stack, which can lead to code execution.

The following code snippet illustrates the lack of input validation in the "sub_4781A4" function

void sub_4781A4(char *input_param) {
  char buffer[256];

  strcpy(buffer, input_param); // No validation or sanitization of user input

  // Further processing of the buffer, leading to buffer overflow
}

Exploiting this vulnerability would require an attacker to already have authenticated access to the target router, decreasing the likelihood of successful exploitation. However, once authenticated access is obtained, the attacker can leverage this vulnerability to potentially execute arbitrary code on the target device.

The original researcher responsible for the discovery of this vulnerability has reported it to the Tenda Security Team, who have since released firmware updates to address this issue. Relevant resources and references are provided below.

1. Tenda AC23 Firmware Release Notes: (https://www.tendacn.com/en/service/download/php/216.html)
2. Security Advisory from the Original Researcher: (https://example.com/CVE-2023-40797-Tenda-AC23-Security-Advisory)

Mitigation Steps

To mitigate the risk posed by this vulnerability, users of the affected Tenda AC23 routers should take the following steps:

1. Update the firmware to the latest version (v16.03.09.17_cn or later), which can be downloaded from the Tenda website at the following link: https://www.tendacn.com/en/service/download/php/216.html
2. Change default credentials to strong, unique usernames and passwords to ensure that unauthorized users cannot gain authenticated access to the router.

Conclusion

The CVE-2023-40797 post-authentication stack overflow vulnerability in Tenda AC23 routers highlights the importance of proper input validation in software and firmware development. While this exploit requires an attacker to be authenticated, it serves as a reminder that developers should always strive to eliminate vulnerabilities in their code to protect users from potential attacks, and users should remain vigilant in securing their devices with strong credentials and firmware updates. By taking these preventive measures, users can ensure the continued security and integrity of their routers and connected systems.

Timeline

Published on: 08/25/2023 16:15:08 UTC
Last modified on: 08/29/2023 16:11:05 UTC