In this post, we are going to take a closer look at CVE-2023-40100, a recently discovered security vulnerability found in the discovery_thread of Dns64Configuration.cpp. This vulnerability, a possible memory corruption due to a use after free, can lead to a local escalation of privilege with no additional execution privileges needed. More importantly, user interaction is not required for exploiting this vulnerability.

To better understand and explore the vulnerability, we will break down the details of the issue at hand, discuss related code snippets, analyze the exploit, and review links to original references.

Background

A use after free vulnerability refers to a situation where a program continues to utilize memory after it has been freed, allowing an attacker to corrupt memory and potentially escalate privileges. In this case, the discovery_thread found in the Dns64Configuration.cpp file is responsible for the problematic code.

Let's take a look at the vulnerable code snippet in Dns64Configuration.cpp

void Dns64Configuration::discovery_thread() {
    std::unique_lock<std::mutex> lock(mStateLock);

    while (mState != State::STOPPING) {
        auto past = std::chrono::steady_clock::now();
        int res = res_nquery(mResState, mQueryname.c_str(), C_IN, T_AAAA, mResponse.data(),
                             mResponse.size());
        if (res != -1) {
            mResponse.resize(res);
            if (parseResponse()) {
                setConfiguration();
            }
        }
        // ...
    }
}

Analysis of Vulnerability

The issue arises when the Dns64Configuration object is freed while the discovery_thread is still executing. Due to the std::unique_lock<std::mutex> within the function, the thread can ensure that it has safe access to the Dns64Configuration object, but it does not guarantee the same safety after the lock is released.

if (parseResponse()) ...;

However, when the object is freed, the memory containing mResponse and mResState might have been allocated for another purpose, leading to potential memory corruption.

Exploit Details

An attacker can exploit this vulnerability by triggering the free of the Dns64Configuration object while the discovery_thread() function is still executing. Given that no additional execution privileges are required and user interaction is not needed for exploitation, this vulnerability presents a significant risk.

1. The full disclosure of CVE-2023-40100 can be found at the official CVE database: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-40100
2. The National Vulnerability Database (NVD) provides more information on the vulnerability's impact, as well as its CVSS v3. base score: https://nvd.nist.gov/vuln/detail/CVE-2023-40100

Conclusion

In conclusion, the memory corruption vulnerability (CVE-2023-40100) found in the discovery_thread of Dns64Configuration.cpp has the potential to allow an attacker to escalate privileges locally through a use after free situation. The vulnerability stems from improper handling of memory in the function, enabling an attacker to exploit the application without user interaction. Understanding the root cause and potential impact is crucial in developing appropriate patches to secure applications and systems from these types of vulnerabilities.

Timeline

Published on: 02/15/2024 23:15:07 UTC
Last modified on: 02/16/2024 13:38:00 UTC