CVE-2024-40674: Uncovering a Denial of Service Vulnerability in validateSsid of WifiConfigurationUtil.java

In this post, we will discuss a recently discovered vulnerability affecting the validateSsid method of WifiConfigurationUtil.java. This vulnerability, assigned as CVE-2024-40674, potentially allows an attacker to overflow a system configuration file, leading to a local denial of service (DoS) attack. The attacker does not need any additional permissions, and user interaction is not required for the exploit to work.

CVE-2024-40674 Explained

The vulnerability resides in the validateSsid method of the WifiConfigurationUtil.java file, which is part of the Android Open Source Project (AOSP). The file is responsible for validating the configuration of Wi-Fi networks in the system. The vulnerability stems from a logic error in the code that could be exploited, leading to the overflow of a system configuration file.

Code Snippet

Here is a snippet of the problematic code in the validateSsid method of WifiConfigurationUtil.java (the complete file can be found on the Android Open Source Project Repository):

public static boolean validateSsid(String ssid, boolean isAsciiAllowed) {
    if (TextUtils.isEmpty(ssid)) {
        return false;
    }

    if (isAsciiAllowed) {
        try {
            ssid.getBytes(StandardCharsets.US_ASCII);
        } catch (IllegalArgumentException e) {
            return false;
        }
    } else {
...

As we can see in the code snippet above, there is no limit on how long the SSID string can be when it is being processed by the validateSsid method. The missing size check for the string leads to the logic error that opens the exploit window.

Exploit Details

To exploit this vulnerability, an attacker could create and broadcast a Wi-Fi network with a specially crafted SSID containing an excessively long string. When the device encounters this Wi-Fi network, it will attempt to store the SSID information in the system configuration file. However, due to the lack of validation for the SSID length in the validateSsid method, this can lead to the overflow of the file, causing a denial of service condition on the targeted device.

Affected Versions

This vulnerability affects Android Open Source Project (AOSP) version 11 and earlier. Devices running unpatched versions of these systems are at risk of encountering this exploit.

Mitigating the Vulnerability

To fix this issue, it's necessary to introduce a limit on the allowable length of the SSID string within the validateSsid method. An update to address this issue was released, and the patch can be found in the Android Open Source Project Repository. It is advised to update affected devices to patched firmware versions as soon as possible.

Conclusion

The CVE-2024-40674 vulnerability highlights the importance of implementing proper input validation in programming. A simple logic error in the code of the validateSsid method has opened the door for a potentially damaging Denial of Service attack. Device manufacturers and users must remain vigilant in maintaining timely updates to protect against potential malicious exploits of devices.

Timeline

Published on: 01/28/2025 20:15:49 UTC
Last modified on: 02/03/2025 16:15:32 UTC