CVE-2021-21309 : Exploit Details and Defense Strategies

A detailed overview of CVE-2021-21309 focusing on an integer overflow vulnerability in 32-bit systems affecting Redis.

Understanding CVE-2021-21309

This section delves into the impact, technical details, and mitigation strategies related to the integer overflow vulnerability in 32-bit systems discovered in Redis.

What is CVE-2021-21309?

CVE-2021-21309 is an integer overflow vulnerability affecting Redis, an open-source, in-memory database. Exploitation of this bug in 32-bit Redis versions 4.0 or newer can lead to heap corruption and potential remote code execution.

The Impact of CVE-2021-21309

The vulnerability poses a medium severity risk with a CVSS base score of 5.4. While it requires high attack complexity, it can be exploited over a network without user interaction, potentially leading to remote code execution.

Technical Details of CVE-2021-21309

This section covers the vulnerability description, affected systems and versions, as well as the exploitation mechanism of CVE-2021-21309.

Vulnerability Description

The integer overflow bug arises in 32-bit Redis versions 4.0 or newer, potentially resulting in buffer overflow and heap corruption. By altering the default configuration settings, authenticated users can make the system vulnerable to exploitation.

Affected Systems and Versions

Redis versions prior to 5.0.11 and 6.0.11 are vulnerable. Specifically, Redis versions less than 5.0.11 and versions greater than or equal to 6.0.0, up to version 6.0.11 are affected by this vulnerability.

Exploitation Mechanism

Exploitation involves triggering integer overflow scenarios by exceeding the maximum supported bulk input size, leading to heap corruption and possible remote code execution.

Mitigation and Prevention

In this section, we explore immediate steps to take to secure Redis systems, long-term security practices, and the importance of patching and updates.

Immediate Steps to Take

It is crucial to update Redis to versions 5.0.11, 6.0.11, or 6.2 to mitigate this vulnerability. Additionally, limiting client access to

CONFIG SET

can help prevent exploitation.

Long-Term Security Practices

Implementing Access Control Lists (ACLs) from Redis version 6.0 onwards and renaming the

CONFIG SET

command in older versions are recommended long-term security practices.

Patching and Updates

Regularly applying security patches and updates released by Redis is essential to secure systems against known vulnerabilities like CVE-2021-21309.