CVE-2021-32626 Explained : Impact and Mitigation
Learn about CVE-2021-32626, a critical security vulnerability in Redis that allows Lua scripts to overflow the heap-based Lua stack. Understand the impact, affected versions, and mitigation steps.
Redis, an open-source, in-memory database, is vulnerable to a critical security issue where specially crafted Lua scripts can overflow the heap-based Lua stack. This vulnerability can potentially lead to heap corruption and remote code execution. The affected versions include Redis versions with Lua scripting support starting from 2.6. Immediate patching is recommended to mitigate the risk.
Understanding CVE-2021-32626
This section provides an in-depth analysis of the CVE-2021-32626 vulnerability affecting Redis.
What is CVE-2021-32626?
CVE-2021-32626 highlights a critical vulnerability in Redis that allows heap-based Lua stack overflow through malicious Lua scripts. This security flaw can result in heap corruption and potentially enable attackers to execute remote code on the affected systems.
The Impact of CVE-2021-32626
The impact of CVE-2021-32626 is severe, with a CVSS v3.1 base score of 7.5 (High). Attackers can exploit this vulnerability remotely, leading to a compromise of confidentiality, integrity, and availability of the Redis instances. The attack complexity is high, with low privileges required for exploitation.
Technical Details of CVE-2021-32626
In this section, we delve into the technical aspects of the CVE-2021-32626 vulnerability in Redis.
Vulnerability Description
The vulnerability arises from incomplete checks in Redis, enabling the execution of malicious Lua scripts that overflow the heap-based Lua stack. This security flaw affects Redis versions with Lua scripting support, beginning from 2.6.
Affected Systems and Versions
The vulnerability impacts Redis versions >= 6.2.0 and < 6.2.6, >= 6.0.0 and < 6.0.16, and >= 2.6.0 and < 5.0.14. Users running these versions are at risk of exploitation and are advised to apply patches immediately.
Exploitation Mechanism
Attackers can exploit this vulnerability by leveraging specially crafted Lua scripts to trigger the heap-based Lua stack overflow. Successful exploitation can lead to heap corruption and potential remote code execution on the target system.
Mitigation and Prevention
To safeguard systems from CVE-2021-32626, immediate actions need to be taken to reduce the exposure to this critical vulnerability.
Immediate Steps to Take
Users are urged to update their Redis installations to the patched versions 6.2.6, 6.0.16, or 5.0.14. If immediate patching is not feasible, a temporary workaround involves restricting the execution of Lua scripts by using ACL to limit EVAL and EVALSHA commands.
Long-Term Security Practices
Implementing a robust security posture that includes regular security updates, network segmentation, and least-privilege access can reduce the overall risk of security vulnerabilities like CVE-2021-32626.
Patching and Updates
Stay informed about security advisories and updates released by Redis to address security vulnerabilities promptly. Regularly applying patches and updates is critical to maintaining a secure Redis environment.