CVE-2021-42389 : Exploit Details and Defense Strategies

Clickhouse is affected by a divide-by-zero vulnerability in its Delta compression codec. Attackers can exploit this issue by crafting a malicious query leading to a divide-by-zero error in processing compressed buffers.

Understanding CVE-2021-42389

Clickhouse, developed by Yandex, is susceptible to a critical vulnerability due to a divide-by-zero error in its compression codec.

What is CVE-2021-42389?

The vulnerability in Clickhouse stems from a divide-by-zero flaw in the Delta compression codec. When a malicious query triggers this issue, the first byte of the compressed buffer undergoes a modulo operation without proper validation.

The Impact of CVE-2021-42389

The impact of CVE-2021-42389 is significant:

CVSS Base Score: 6.5 (Medium)
Attack Vector: Network
Availability Impact: High
Privileges Required: Low
Attack Complexity: Low

Technical Details of CVE-2021-42389

Clickhouse's vulnerability requires a closer look at its technical aspects.

Vulnerability Description

The vulnerability allows attackers to exploit a divide-by-zero error in Clickhouse's Delta compression codec when processing a malicious query. This results in a modulo operation using the first byte of the compressed buffer without checking for a zero value.

Affected Systems and Versions

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

Exploitation Mechanism

The exploitation of this vulnerability involves crafting a malicious query that triggers the divide-by-zero error within the Delta compression codec of Clickhouse.

Mitigation and Prevention

Protecting systems from CVE-2021-42389 requires immediate action and long-term security practices.

Immediate Steps to Take

Update Clickhouse to version 21.10.2.15-stable or higher to mitigate the vulnerability.
Monitor and restrict network access to Clickhouse instances.
Deploy network intrusion detection systems to identify potential exploitation attempts.

Long-Term Security Practices

Conduct regular security audits and code reviews to identify and address potential vulnerabilities.
Educate developers and system administrators about secure coding practices and threat awareness.
Implement strict input validation mechanisms to prevent malicious queries.

Patching and Updates

Apply security patches promptly to ensure all known vulnerabilities, including CVE-2021-42389, are addressed.