CVE-2021-39185 : What You Need to Know

Http4s is a minimal, idiomatic Scala interface for HTTP services. In http4s versions 0.21.26 and prior, 0.22.0 through 0.22.2, 0.23.0, 0.23.1, and 1.0.0-M1 through 1.0.0-M24, the default CORS configuration is vulnerable to an origin reflection attack. Learn more about the impact, technical details, and mitigation strategies below.

Understanding CVE-2021-39185

HTTP4s vulnerability in default CORS configuration enabling any origin with credentials.

What is CVE-2021-39185?

HTTP4s versions affected by a default CORS configuration vulnerability allowing an origin reflection attack.

The Impact of CVE-2021-39185

This vulnerability has a base severity rating of CRITICAL with a CVSS base score of 9.1. It can lead to high confidentiality and integrity impact without requiring privileges or user interaction.

Technical Details of CVE-2021-39185

Details on the vulnerability and affected systems.

Vulnerability Description

The default CORS configuration in vulnerable HTTP4s versions permits any origin with credentials, potentially leading to security risks like an origin reflection attack.

Affected Systems and Versions

Versions < 0.21.27
Versions >= 0.22.0, < 0.22.3
Versions >= 0.23.0, < 0.23.2
Versions >= 1.0.0-M1, <= 1.0.0-M24

Exploitation Mechanism

The vulnerability allows attackers to exploit the default CORS configuration to perform an origin reflection attack, compromising the security of the system.

Mitigation and Prevention

Actions to mitigate and prevent exploitation of CVE-2021-39185.

Immediate Steps to Take

Upgrade HTTP4s to fixed versions: 0.21.27, 0.22.3, 0.23.2, 1.0.0-M25
Implement alternative CORS configurations to secure HTTP services

Long-Term Security Practices

Regularly update and patch HTTP4s to the latest versions
Monitor security advisories and apply recommended security best practices

Patching and Updates

Ensure timely installation of patches and updates provided by HTTP4s to address the vulnerability.