In today's world of growing technology, Wi-Fi has become an essential part of our daily lives. With the widespread use of wireless networks, security vulnerabilities have become more crucial than ever. One such vulnerability is the buffer overwrite flaw, a dangerous issue that can lead to a complete system compromise.

In this long read post, we will delve into the details of the CVE-2017-15832 vulnerability, a buffer overwrite in the WLAN Host Driver. We will analyze the vulnerable code, provide code snippets, discuss its exploit details, and offer links to references for further information.

Overview of CVE-2017-15832

CVE-2017-15832 is a critical vulnerability that affects the WLAN host driver and enables an attacker to execute arbitrary code on a victim's system remotely. This vulnerability arises due to a buffer overwrite on a stack-based buffer in the WLAN host driver when it interacts with a compromised WLAN firmware.

To provide a clear understanding of this vulnerability, let's dive into the problematic code snippet

// Vulnerable function in the host driver
void process_cmd_response(struct wlan_resp *resp) {
    char buffer[128];
    
    // ... some code ...
    
    // Vulnerable line
    memcpy(buffer, resp->data, resp->length);
    
    // ... some more code ...
}

Here, the process_cmd_response() function takes a pointer to a wlan_resp struct as input and extracts the response data to copy it into a local buffer. The vulnerability occurs when the memcpy() function does not check whether the length of data in resp->data is smaller than the size of the buffer, causing a buffer overwrite.

Exploit Details

To successfully exploit this vulnerability, an attacker has to leverage a compromised WLAN firmware to send a crafted response that contains data larger than the fixed buffer size. Let's consider an example of how an attacker could exploit this flaw:

Attacker compromises the WLAN firmware by using existing vulnerabilities or physical access.

2. Attacker prepares a malicious response that contains 140 bytes of data, while the fixed buffer size is only 128 bytes.

The target system's WLAN host driver receives the malicious response from the compromised firmware.

4. Due to the buffer overwrite, the extra data (12 bytes, in this example) corrupts other memory objects, which could lead to arbitrary code execution or denial of service.

This exploit's impact can vary depending on the overwritten memory objects and the attacker's ability to control the data that overwrites the buffer.

Mitigation

The best way to mitigate this vulnerability is to verify if the length of data to be copied from resp->data is smaller than the size of the buffer before using the memcpy() function. A sample code patch is shown below:

// Fixed function in the host driver
void process_cmd_response(struct wlan_resp *resp) {
    char buffer[128];
    
    // ... some code ...

    // Fixed line: Check length before performing memcpy
    if (resp->length <= sizeof(buffer)) {
        memcpy(buffer, resp->data, resp->length);
    }
    
    // ... some more code ...
}

Furthermore, updating the firmware and the host driver to the latest version and applying security patches can aid in preventing such vulnerabilities.

Conclusion

Security vulnerabilities like the CVE-2017-15832 buffer overwrite are of great significance as they can lead to severe consequences if exploited by attackers. In this post, we have explored the vulnerable code, its details, and its exploitation. Staying informed about such vulnerabilities and taking prompt mitigation actions is crucial to ensuring the security of connected devices and networks.

For original references and more information, consider reviewing these resources

1. "CVE-2017-15832", NIST National Vulnerability Database (NVD), https://nvd.nist.gov/vuln/detail/CVE-2017-15832
2. Seunghun Han, " 디버퍼 오버플로우를 이용한 이론적인 공격 사례", System Security Research Lab, https://seunghunhan.tistory.com/10 (in Korean)
3. "OWASP - Buffer Overflow Attack", Open Web Application Security Project (OWASP), https://owasp.org/www-community/attacks/Buffer_overflow_attack
4. "A Guide to Preventing Buffer Overflow Attacks", SectigoStore, https://sectigostore.com/blog/buffer-overflow-attacks

Timeline

Published on: 11/26/2024 09:15:04 UTC