CVE-2022-44259 - Exploring the Post-authentication Buffer Overflow in TOTOLINK LR350 V9.3.5u.6369_B20220309: Exposure, Exploitation, and Mitigation

TOTOLINK, a known manufacturer of networking devices, has a vulnerability in its LR350 router with firmware version 9.3.5u.6369_B20220309. The issue, identified as CVE-2022-44259, is a post-authentication buffer overflow that exists within the setParentalRules function, and it can be triggered by exploiting the parameters "week", "sTime", and "eTime". In this long read, we will dive deep into the vulnerability details, provide code snippets for better understanding, explore potential exploitation scenarios, and discuss possible ways to mitigate the risk. But first and foremost, let's have a brief look at the original references.

NVD - National Vulnerability Database:

https://nvd.nist.gov/vuln/detail/CVE-2022-44259

https://www.totolink.net/

Vulnerability disclosure at Exploit-DB:

https://www.exploit-db.com/exploits/52045

Now, let's break down the vulnerability in detail.

Vulnerability Details

The TOTOLINK LR350 router is susceptible to a post-authentication buffer overflow vulnerability within the setParentalRules function. Attackers able to authenticate to the device can exploit this vulnerability, potentially leading to remote code execution, unauthorized access, or system crashes.

The affected parameters are "week", "sTime", and "eTime". By supplying an overly long input to these parameters, an attacker can overwrite memory, which in turn may cause a buffer overflow. To better illustrate the issue, let's examine a code snippet representing the vulnerable function:

void setParentalRules(char *parameters)
{
  char week[8];
  char sTime[6];
  char eTime[6];
  
  // ... Parsing the input parameters ...

  strcpy(week, getParameterValue(parameters, "week")); // Buffer overflow if "week" is too long
  strcpy(sTime, getParameterValue(parameters, "sTime")); // Buffer overflow if "sTime" is too long
  strcpy(eTime, getParameterValue(parameters, "eTime")); // Buffer overflow if "eTime" is too long

  // ... Setting the parental rules ...
}

In the code above, the setParentalRules function begins by declaring three character arrays week, sTime, and eTime. Then it copies the values from the input parameters which an attacker provides. If these input values are longer than the allocated buffer size, strcpy() will overwrite the memory, causing a buffer overflow.

Exploitation

An attacker who has authenticated access to the device can create a specially crafted HTTP request to the setParentalRules function, providing malicious input for the "week", "sTime", and "eTime" parameters. This may enable the attacker to cause buffer overflow, leading to remote code execution or unauthorized access, depending on the vulnerability's actual exploitation capabilities.

Below is an example of an HTTP request that may be used to exploit this vulnerability

POST /setParentalRules HTTP/1.1
Host: vulnerable.router
User-Agent: Mozilla/5.
Content-Type: application/x-www-form-urlencoded
Cookie: authorized=yes

week=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA&
sTime=BBBBBBBBBBBBBBBBBBBB&
eTime=CCCCCCCCCCCCCCCCCCCC

Mitigation

To mitigate the risk associated with this vulnerability and protect your device from potential exploitation, consider taking the following actions:

1. Regularly update the router's firmware to the latest available version (especially if TOTOLINK releases an update addressing this particular vulnerability).

2. Change the default router credentials to unique and strong ones to prevent unauthorized access and authentication.

3. Restrict remote access to the router's administration interface, and only allow trusted local network devices to interact with the management functions.

4. Keep an eye on the latest security news and router vulnerability disclosures to stay informed and prepared.

Conclusion

CVE-2022-44259 is a critical post-authentication buffer overflow vulnerability in TOTOLINK LR350 routers with firmware version 9.3.5u.6369_B20220309. It affects the setParentalRules function and can be triggered using malicious input for parameters "week", "sTime", and "eTime". Users should follow the recommended mitigation measures to defend their routers against potential exploitation. Staying informed of the latest security developments, promptly updating firmware, and adopting better security practices are the best ways to stay protected against such vulnerabilities.

Timeline

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