CVE-2021-42390 : What You Need to Know

A Divide-by-zero vulnerability in Clickhouse's DeltaDouble compression codec can be exploited by parsing a malicious query, potentially leading to denial of service.

Understanding CVE-2021-42390

What is CVE-2021-42390?

The CVE-2021-42390 vulnerability involves a divide-by-zero issue in Clickhouse's DeltaDouble compression codec when processing a malicious query, where the first byte of the compressed buffer is used in a modulo operation without checking for zero.

The Impact of CVE-2021-42390

This vulnerability has a CVSS base score of 6.5 (Medium) with a high availability impact. It can be exploited remotely with low privileges required, potentially causing a denial of service.

Technical Details of CVE-2021-42390

Vulnerability Description

The vulnerability lies in the handling of a compressed buffer's first byte within Clickhouse's DeltaDouble compression codec, allowing a divide-by-zero scenario.

Affected Systems and Versions

Product: Clickhouse
Vendor: Yandex
Version: < 21.10.2.15-stable (custom)

Exploitation Mechanism

A threat actor can exploit this vulnerability by sending a specially crafted query to a system using the affected version, triggering the divide-by-zero condition.

Mitigation and Prevention

Immediate Steps to Take

Update Clickhouse to a patched version (21.10.2.15-stable or later).
Monitor network traffic for any unusual activities that could indicate exploitation attempts.

Long-Term Security Practices

Regularly review and update security configurations and best practices for database systems.
Conduct security assessments and penetration testing to identify and address vulnerabilities.

Patching and Updates

Apply vendor-supplied patches promptly to address security vulnerabilities and protect systems from exploitation.