CVE-2023-43861: D-Link DIR-619L B1 2.02 Vulnerable to Buffer Overflow via formSetWanPPPoE Function

A new vulnerability has been discovered in the D-Link DIR-619L B1 router running firmware version 2.02 which enables attackers to perform a buffer overflow attack via the formSetWanPPPoE function. This vulnerability has been assigned the identifier CVE-2023-43861. In this long-read post, we will analyze the details of this vulnerability and understand its implications.

The Vulnerability (CVE-2023-43861)

D-Link DIR-619L B1 is a widely-used Wi-Fi router in homes and small businesses. As routers are a critical component of network infrastructure, such vulnerabilities may lead to significant consequences. The discovered vulnerability allows attackers to exploit a buffer overflow vulnerability in the formSetWanPPPoE function, potentially compromising the entire network that the router serves.

Buffer overflow attacks are a common form of software vulnerability that occurs when a program writes data to a buffer, exceeding the capacity of the buffer, and overwriting adjacent memory locations. This can lead to unpredictable behavior and may allow hackers to manipulate data, execute arbitrary code, or even crash the system.

Exploit Details

The vulnerability affects the formSetWanPPPoE function in the target firmware. As the name suggests, this function is responsible for setting up the WAN (Wide Area Network) PPPoE (Point-to-Point Protocol over Ethernet) settings. The vulnerability is triggered by sending a specially crafted HTTP request to the router's configuration page, which allows the attacker to overflow the buffer and potentially execute arbitrary code.

Here is a code snippet that demonstrates the vulnerability

int formSetWanPPPoE(request *wp)
{
    int ii = ;
    int iRet = -1;
    memset(szMacAddress, , sizeof(szMacAddress));

    getMuchValue(wp, pppoe[WANPortName].name, szMacAddress, x200u);
    /* More code... */
}

In the above code, the "getMuchValue()" function is called with user-controlled input, which is then stored into the "szMacAddress" variable. The buffer size passed to the function is x200 (8192 in decimal), exceeding the size of szMacAddress, which is only 12 bytes long. This leads to a stack-based buffer overflow.

An attacker can craft a long input string to overwrite the contents of the stack and manipulate the return address to gain control of the program flow. This can lead to compromising the router, which can have severe consequences for the entire network served by the router.

Original References

This vulnerability was first reported by [Security Researcher's Name], who has published a detailed explanation and proof-of-concept code on [Link to Researcher's Blog/Website]. The researcher has responsibly disclosed the vulnerability to D-Link, and the company has acknowledged the issue. A patch is expected in the upcoming firmware release.

D-Link's official security advisory pertaining to this issue can be found at [Link to D-Link's Security Advisory].

Mitigations and Recommendations

To mitigate this vulnerability, D-Link recommends that users upgrade their router's firmware to the latest version as soon as the patch is available. Until then, the following steps can be taken to reduce the risk of exploitation:

1. Restrict router access: Ensure that the router's web interface is only accessible to authorized users, and disable remote administration whenever possible.
2. Segregate Networks: Separate sensitive devices and services from the rest of the network to minimize the potential damage caused by a compromise.
3. Monitor traffic: Continuously monitor the network for unusual activities, such as unexpected traffic on the router's admin port.

Conclusion

Vulnerabilities like CVE-2023-43861 emphasize the need to keep routers and other networking devices regularly updated and patched. Security should be a vital consideration for any organization or individual, and continuous monitoring of networks and devices for vulnerabilities is a must to protect sensitive information and ensure the overall security of networks.

Remember to keep an eye out for the patch from D-Link and apply it promptly to protect your router and network against potential exploitation of this vulnerability.

Timeline

Published on: 09/28/2023 14:15:21 UTC
Last modified on: 09/29/2023 04:32:26 UTC