CVE-2021-42388 : Security Advisory and Response

CVE-2021-42388, published on 2022-03-14, involves a heap out-of-bounds read vulnerability in Clickhouse's LZ4 compression codec. This issue allows for potential exploitation when processing specific queries.

Understanding CVE-2021-42388

What is CVE-2021-42388?

The CVE-2021-42388 vulnerability in Clickhouse's LZ4 compression codec occurs during the parsing of a malicious query. It happens due to improper validation of user-supplied data leading to a heap out-of-bounds read.

The Impact of CVE-2021-42388

The vulnerability allows an attacker to read uninitialized or out-of-bound memory, potentially leading to information exposure or denial of service.

Technical Details of CVE-2021-42388

Vulnerability Description

The issue arises when an unsigned 16-bit user-supplied value ('offset') is read from compressed data in the LZ4::decompressImpl() loop, later used in a copy operation without proper bounds checking.

Affected Systems and Versions

Vendor: Yandex
Product: Clickhouse
Affected Version: Unspecified
Versions Affected: Less than 21.10.2.15-stable (Custom Version Type)

Exploitation Mechanism

Attackers can exploit this vulnerability by crafting a malicious query that triggers the out-of-bounds read, potentially leading to further exploitation or disruption.

Mitigation and Prevention

Immediate Steps to Take

Apply the latest security update provided by the vendor to mitigate the vulnerability.
Monitor security mailing lists and advisories for any additional guidance or patches.

Long-Term Security Practices

Implement input validation mechanisms to prevent malformed queries from reaching critical processing components.
Conduct regular security assessments and audits to identify and remediate potential vulnerabilities.

Patching and Updates

It is crucial to regularly update software components, especially security patches, to address known vulnerabilities and enhance system security.