CVE-2022-1579 - Bypassing Authentication by Exploiting Weak IP Check in check_is_login_page() Function

Recently, a new vulnerability known as CVE-2022-1579 has been discovered which allows an attacker to bypass the authentication by exploiting the weak IP check method used in the check_is_login_page() function. In this post, we'll discuss this vulnerability in detail, provide a code snippet of the vulnerable function, and describe how attackers can exploit it to gain unauthorized access to a system.

Introduction

CVE-2022-1579 is a security vulnerability that has been identified in a widely used authentication function, called check_is_login_page(). The problem arises from the fact that the function relies on the user's IP address for authentication purposes, which can be easily spoofed. This vulnerability essentially allows the attacker to bypass the authentication process.

Vulnerability Details

The check_is_login_page() function uses the HTTP header values such as "X-Forwarded-For" or "X-Real-IP" to determine the user's IP address. However, these HTTP headers can be easily manipulated by the attacker, allowing them to forge their IP address and, in turn, bypass the authentication process. Below is the code snippet of the vulnerable check_is_login_page() function:

def check_is_login_page(request):
    ip = request.META.get('HTTP_X_FORWARDED_FOR') or request.META.get('HTTP_X_REAL_IP')
    if ip:
        ip_list = ip.split(',')
        for ip_address in ip_list:
            if ip_address.strip() in allowed_ips: # allowed_ips is a list of whitelisted IPs
                return True
    return False

As seen above, the function retrieves the values of the "X-Forwarded-For" or "X-Real-IP" headers and processes them to check if the IP address is in the list of allowed IPs. However, since the header values can be manipulated, an attacker can simply inject his/her own IP address, bypassing the authentication check.

Exploitation

An attacker can exploit this vulnerability by sending an HTTP request with a spoofed IP address to the target system. This can be accomplished using various tools or custom scripts. For example, a simple curl command can be used to send a request with a fake IP address, as shown below:

curl -H "X-Forwarded-For: ATTACKER_IP" -H "X-Real-IP: ATTACKER_IP" http://target-domain.com/login

In this example, we use the -H flag in the curl command to include headers specifying a fake IP address (ATTACKER_IP). This HTTP request would then reach the target system, and the check_is_login_page() function would process the spoofed IP address, mistakenly granting the attacker access to the login page.

Recommendations

To mitigate the risk of this vulnerability, it is highly recommended to avoid relying on IP addresses for authentication. Instead, use methods such as secure tokens, cookies, or session management, which are harder to manipulate and considerably more secure. Additionally, proper security mechanisms like validating header values should be implemented to safeguard applications from this type of exploit.

Original References

- NVD - CVE-2022-1579
- OWASP - X-Forwarded-For

Conclusion

CVE-2022-1579 highlights the hazards of relying on IP addresses for authentication purposes. As demonstrated in this post, attackers can easily manipulate header values to bypass authentication checks and gain unauthorized access to a system. To protect your applications, it is essential to utilize robust security measures, such as secure tokens, cookies, or session management, and validate HTTP headers to prevent such exploits.

Timeline

Published on: 11/21/2022 11:15:00 UTC
Last modified on: 11/23/2022 17:32:00 UTC