In this post, we will discuss a recently disclosed vulnerability (CVE-2024-24790) affecting the handling of IPv4-mapped IPv6 addresses, resulting in the unexpected behavior of the various "Is" methods (IsPrivate, IsLoopback, etc.) in certain networking components. The flaw resides in how the affected "Is" methods return values for IPv4-mapped IPv6 addresses. We will also provide a code snippet demonstrating the issue, links to original references, and details regarding potential exploits.

Vulnerability Details

IPv6 is the latest version of the Internet Protocol designed to replace IPv4. Given the massive number of devices connected to the Internet today and consequently, the exhaustion of available IPv4 addresses, IPv6 has been devised to handle the ongoing demand for IP addresses. One key aspect of IPv6 is its ability to map certain IPv4 addresses to IPv6 via a special representation known as IPv4-mapped IPv6 addresses.

Now, let's consider the various "Is" methods (e.g., IsPrivate, IsLoopback, etc.) that are typically used in networking APIs and components. These methods are meant to return correct results for any given IP address, be it in IPv4 or IPv6 format.

However, under CVE-2024-24790, it has been observed that these methods do not work as expected for IPv4-mapped IPv6 addresses. Specifically, they return "false" for addresses that would otherwise return "true" in their traditional IPv4 forms.

Here is a simple code snippet that demonstrates the issue in Python

import ipaddress

def test_is_methods(ipv4_addr, ipv6_addr):
    print(f'Is private for {ipv4_addr}:', ipaddress.ip_address(ipv4_addr).is_private)
    print(f'Is private for {ipv6_addr}:', ipaddress.ip_address(ipv6_addr).is_private)
    print(f'Is loopback for {ipv4_addr}:', ipaddress.ip_address(ipv4_addr).is_loopback)
    print(f'Is loopback for {ipv6_addr}:', ipaddress.ip_address(ipv6_addr).is_loopback)

ipv4_address = '192.168.1.1'
ipv6_mapped_address = '::ffff:192.168.1.1'

test_is_methods(ipv4_address, ipv6_mapped_address)

The output of the above code snippet will be

Is private for 192.168.1.1: True
Is private for ::ffff:192.168.1.1: False
Is loopback for 192.168.1.1: False
Is loopback for ::ffff:192.168.1.1: False

As you can see, when the same IP address is in their traditional IPv4 form (192.168.1.1) and IPv4-mapped IPv6 form (::ffff:192.168.1.1), the "Is" methods return different results.

- Official CVE Details

- NIST National Vulnerability Database (NVD) Entry

Exploit Details

An attacker may exploit this vulnerability by manipulating the input data being processed within an application's networking components. By doing so, the attacker might bypass security checks, gain unauthorized access to resources, or even execute attacks like denial of service (DoS).

For instance, applications that rely solely on the "Is" methods to validate IP addresses for access control or rate-limiting could be potentially exploited. If an attacker sends carefully crafted IPv4-mapped IPv6 addresses, this may bypass such restrictions, allowing them to gain unauthorized access or perform DDoS attacks.

Conclusion

CVE-2024-24790 highlights a significant vulnerability in the way "Is" methods handle IPv4-mapped IPv6 addresses. It is essential for developers and system administrators to be aware of this flaw and ensure their applications implement proper input validation and security checks, considering both IPv4 and IPv6 formats, to mitigate any potential risks.

Timeline

Published on: 06/05/2024 16:15:10 UTC
Last modified on: 06/18/2024 17:59:12 UTC