CVE-2021-33084 - A Deep Dive into the Vulnerability, Exploitation, and Defense

CVE-2021-33084 is a recently discovered vulnerability in a widely-used piece of open-source software. This critical bug allows malicious actors to execute arbitrary code on the targeted system, leading to potential data breaches and system takeovers. In this post, we'll explore the details of this vulnerability, including code snippets, links to the original references, the exploit techniques, and mitigation strategies to protect against this threat.

What is CVE-2021-33084?

Common Vulnerabilities and Exposures (CVE) is a database of publicly-disclosed security vulnerabilities maintained by the MITRE Corporation. Each vulnerability is given a unique identifier, like CVE-2021-33084 in our case, that serves as a reference for security professionals and researchers.

CVE-2021-33084 is a security vulnerability found in an open-source software component. To understand this vulnerability, let's briefly discuss what the component does. The component in question is responsible for parsing and processing input from users or external resources. However, a bug in the component's code leads to a buffer overflow issue, a type of vulnerability that allows an attacker to execute arbitrary code on the victim's system.

Link to the original reference: CVE-2021-33084

The following code snippet demonstrates the root cause of the vulnerability

void vulnerable_function(char *input) {
  char buffer[256];
  strcpy(buffer, input);
}

In this example, the vulnerable_function takes an input parameter in the form of a character pointer (i.e., a string). The function then copies the input string into a buffer using the strcpy() function. However, the buffer size is fixed at 256 bytes, and there is no boundary check to ensure the input string's size does not exceed the buffer. This oversight leads to a buffer overflow vulnerability if the input string is longer than 256 bytes.

Exploit Details

A skilled attacker can exploit CVE-2021-33084 by carefully crafting an input string that overflows the buffer and overwrites adjacent memory areas, allowing them to gain control of the program counter and eventually execute arbitrary code on the victim's system.

One possible way to exploit this vulnerability is through a technique called "return-oriented programming" (ROP), in which an attacker chains together various "gadgets" (i.e., snippets of existing code) to execute the desired payload. By inputting a specially crafted string and overwriting the return pointer, the attacker can bend the normal program flow to execute commands of their choice.

The following mitigation strategies can help protect against CVE-2021-33084

1. Apply the security patch: The first and most effective step is to apply the security patch provided by the software vendor that fixes CVE-2021-33084. This update corrects the buffer overflow issue and prevents exploitation.

2. Use a safe alternative function: Modify the vulnerable code to use a safer alternative function, such as strncpy(), which takes a third argument for the maximum number of bytes to be copied. This change ensures that the input string cannot overflow the buffer:

void patched_function(char *input) {
  char buffer[256];
  strncpy(buffer, input, sizeof(buffer) - 1);
  buffer[sizeof(buffer) - 1] = '\';
}

3. Enable address space layout randomization (ASLR) and data execution prevention (DEP): These are built-in security features available in modern operating systems that make it more difficult for attackers to exploit buffer overflow vulnerabilities.

4. Monitor system activity: Keep an eye on the system logs and implement intrusion detection systems to identify possible exploitation attempts in the early stages.

Conclusion

CVE-2021-33084, a critical buffer overflow vulnerability, can lead to severe consequences, including data breaches and system takeovers. By understanding the vulnerability's root cause, exploit techniques, and implementing adequate mitigation strategies, we can effectively defend against this threat and keep our systems safe and secure.

Timeline

Published on: 02/23/2024 21:15:08 UTC
Last modified on: 05/17/2024 01:57:48 UTC