CVE-2024-6874: Stack Buffer Overflow Vulnerability in libcurl's URL API Function (curl_url_get)

A stack buffer overflow vulnerability has been discovered in libcurl's URL API function, curl_url_get(). This vulnerability allows attackers to potentially execute arbitrary code, crash applications, or leak sensitive data. In this post, we will discuss the details of this vulnerability, its root cause, the affected systems, and the potential exploitation techniques. We will also provide suggestions for mitigating the risks associated with the CVE-2024-6874 vulnerability.

Background

libcurl is a popular, open-source library that provides support for various network protocols. One of its core functionalities is to handle URL parsing and manipulation. The curl_url_get() function is a part of the libcurl's URL API and offers punycode conversions to and from Internationalized Domain Names (IDN) when interacting with non-ASCII domain names.

Vulnerability Details

When built to use the *macidn* IDN backend, libcurl's curl_url_get() function has a stack buffer overflow vulnerability. This flaw occurs when converting a name that is exactly 256 bytes long. The conversion function fills up the provided buffer exactly, but it fails to null-terminate the string. As a result, this issue can lead to stack contents accidentally getting returned as part of the converted string.

A code snippet showing the problematic function call can be seen below

int macidn_convert_wrapper(int operation, const char *from, char *to, size_t tolen)
{
    size_t n;
    switch (operation)
    {
        case IDN2_ASCII_U:
        else
        {
            //...
            *tolen = n;
        }
        break;

        case IDN2_UTF8_NFC:
        //...
    }
}

The problem lies in the fact that the provided buffer "to" is not properly null-terminated after the conversion has occurred, leaving it open to read data from outside the buffer's intended boundaries.

Exploitation

Exploiting this vulnerability can have various consequences, including the ability to execute arbitrary code, cause application crashes, or leak sensitive information. By sending a carefully crafted request with a 256-byte domain name, an attacker could potentially exploit this issue and cause stack content to be leaked as part of the converted string.

Affected Systems

This vulnerability affects libcurl versions built to use the *macidn* IDN backend. It is essential to review your specific implementation of libcurl and determine if your system may be affected by CVE-2024-6874.

Mitigation

To mitigate the risks associated with CVE-2024-6874, developers should update their libcurl libraries to the latest available version, which contains a fix for this vulnerability. Additionally, developers should ensure that they are using the most recent version of their IDN backend, as this can help prevent future vulnerabilities.

In conclusion, the CVE-2024-6874 vulnerability is a critical flaw in libcurl's URL API function that could lead to severe security implications. By staying informed about the vulnerability, updating affected systems, and following proper coding practices, developers can mitigate the risks posed by this vulnerability and protect users' data.

Timeline

Published on: 07/24/2024 08:15:03 UTC
Last modified on: 08/01/2024 14:00:45 UTC