CVE-2021-32829 : Exploit Details and Defense Strategies

ZStack, an open-source IaaS software, is vulnerable to a post-authentication Remote Code Execution (RCE) issue due to the bypass of the Groovy shell sandbox. Attackers can exploit this vulnerability through the exposed zstack/v1/batch-queries?script endpoint in the REST API, leading to critical impact.

Understanding CVE-2021-32829

This vulnerability affects ZStack REST API versions < 3.8.21, >=3.10.0 and < 3.10.8, and >=4.0.0 and < 4.1.0. It allows attackers to execute remote code post-authentication by bypassing the Groovy shell sandbox.

What is CVE-2021-32829?

ZStack, an Infrastructure as a Service software, suffers from a post-authentication Remote Code Execution (RCE) vulnerability. The weakness arises due to the inadequate restrictions on user-controlled Groovy scripts within the REST API.

The Impact of CVE-2021-32829

The vulnerability poses a critical threat, leading to post-authenticated remote code execution. It enables attackers to bypass the Groovy shell sandbox in the ZStack REST API, compromising the confidentiality and integrity of the system.

Technical Details of CVE-2021-32829

The vulnerability exists due to the evaluation of user-controlled Groovy scripts in the BatchQuery.query method, where the sandbox fails to restrict code in Java annotations, permitting meta-programming escapes.

Vulnerability Description

The flaw in ZStack's REST API allows for post-authentication RCE by leveraging the script endpoint, potentially executing malicious commands.

Affected Systems and Versions

ZStack versions < 3.8.21, >=3.10.0 and < 3.10.8, and >=4.0.0 to < 4.1.0 are impacted by this vulnerability.

Exploitation Mechanism

Attackers can exploit this issue by crafting a malicious Groovy script within the script parameter of zstack/v1/batch-queries, circumventing the sandbox restrictions.

Mitigation and Prevention

To address CVE-2021-32829, immediate action is required to secure ZStack installations and prevent potential RCE attacks.

Immediate Steps to Take

Upgrade ZStack to versions 3.8.21, 3.10.8, or 4.1.0 to mitigate the vulnerability.
Restrict network access to the ZStack REST API to trusted entities only.

Long-Term Security Practices

Regularly monitor and update ZStack software to include security patches and enhancements.
Conduct security audits to identify and address vulnerabilities in the system.

Patching and Updates

Ensure timely patching of ZStack installations to the latest secure versions to prevent exploitation of known vulnerabilities.