CVE-2022-21656 Explained : Impact and Mitigation

Envoy is an open source edge and service proxy vulnerable to a X.509 subjectAltName matching bypass issue that can lead to improper certificate validation.

Understanding CVE-2022-21656

This CVE highlights a critical security vulnerability in Envoy that allows for the bypassing of name constraints in certificate validation, potentially leading to the impersonation of arbitrary servers.

What is CVE-2022-21656?

CVE-2022-21656 is a vulnerability in Envoy affecting versions lower than 1.20.2. The issue arises from a "type confusion" bug in the default certificate validation routines when processing subjectAltNames.

The Impact of CVE-2022-21656

The vulnerability poses a high severity threat with a CVSS base score of 7.4, allowing attackers to authenticate rfc822Name or uniformResourceIndicator as a domain name, enabling the trust of untrusted upstream certificates.

Technical Details of CVE-2022-21656

This section delves into the specifics of the vulnerability.

Vulnerability Description

The vulnerability in Envoy results from a flaw in the default certificate validation routines, leading to the bypassing of name constraints and potential impersonation of servers.

Affected Systems and Versions

Envoy versions prior to 1.20.2 are vulnerable to this X.509 subjectAltName matching bypass issue.

Exploitation Mechanism

Attackers can exploit this vulnerability to deceive Envoy into trusting unauthorized upstream certificates, enabling potential impersonation attacks.

Mitigation and Prevention

To address CVE-2022-21656, immediate actions and long-term security practices are crucial.

Immediate Steps to Take

Users should update Envoy to version 1.20.2 or later to mitigate the vulnerability. Additionally, carefully monitor certificate validation processes for any suspicious activity.

Long-Term Security Practices

Implement strict certificate validation protocols, regular security audits, and stay informed about security updates and patches.

Patching and Updates

Regularly apply security patches and updates provided by Envoy to safeguard systems against known vulnerabilities.