CVE-2021-3999 : Exploit Details and Defense Strategies

A buffer overflow and underflow vulnerability in glibc's getcwd() function could allow a local attacker to execute arbitrary code and escalate privileges on the system.

Understanding CVE-2021-3999

This section will cover the details of the CVE-2021-3999 vulnerability.

What is CVE-2021-3999?

The CVE-2021-3999 vulnerability involves an off-by-one buffer overflow and underflow in the getcwd() function of glibc. This flaw may result in memory corruption and potentially allow an attacker to execute arbitrary code by controlling the input buffer.

The Impact of CVE-2021-3999

Exploitation of this vulnerability could enable a local attacker to elevate their privileges on the system, posing a significant security risk to affected environments.

Technical Details of CVE-2021-3999

In this section, we will delve into the technical aspects of CVE-2021-3999.

Vulnerability Description

The vulnerability arises due to an off-by-one buffer overflow and underflow in the getcwd() function within glibc library, leading to potential memory corruption.

Affected Systems and Versions

The glibc versions up to v2.31 are impacted by this vulnerability. It has been fixed in glibc versions 2.31 and above.

Exploitation Mechanism

A local attacker who can manipulate the input buffer and size passed to getcwd() in a setuid program could exploit this flaw to execute arbitrary code and escalate their privileges.

Mitigation and Prevention

To secure your systems against CVE-2021-3999, follow the recommended mitigation strategies below.

Immediate Steps to Take

Update glibc to version 2.31 or higher to apply the necessary patch and prevent exploitation of the vulnerability.
Restrict access to vulnerable setuid programs to limit the attack surface.

Long-Term Security Practices

Regularly monitor and apply security updates for glibc and other critical system libraries.
Implement the principle of least privilege to minimize the impact of potential security breaches.

Patching and Updates

Stay informed about security advisories and patches released by glibc maintainers and vendors to address vulnerabilities like CVE-2021-3999.