CVE-2021-3618 : Security Advisory and Response

ALPACA is an application layer protocol content confusion attack that exploits TLS servers implementing different protocols but using compatible certificates, allowing a Man-in-the-Middle (MitM) attacker to redirect traffic from one subdomain to another.

Understanding CVE-2021-3618

ALPACA vulnerability impacts servers using multi-domain or wildcard certificates, potentially leading to cross-protocol attacks.

What is CVE-2021-3618?

CVE-2021-3618, known as ALPACA, undermines TLS authentication by manipulating traffic redirection between subdomains, compromising application layer security.

The Impact of CVE-2021-3618

ALPACA poses a significant threat by bypassing TLS authentication, enabling potential cross-protocol attacks that exploit server vulnerabilities.

Technical Details of CVE-2021-3618

ALPACA impacts versions of vsftpd 3.0.4, nginx 1.21.0, and sendmail 8.17, leading to TLS authentication bypass.

Vulnerability Description

ALPACA allows MitM attackers to redirect traffic between subdomains, breaking TLS authentication and opening the door to cross-protocol attacks.

Affected Systems and Versions

vsftpd 3.0.4, nginx 1.21.0, and sendmail 8.17 are among the affected systems vulnerable to ALPACA's attack.

Exploitation Mechanism

Exploiting ALPACA requires access at the TCP/IP layer to redirect traffic between subdomains, bypassing TLS authentication.

Mitigation and Prevention

Implement immediate steps to secure systems from ALPACA and adopt long-term practices to enhance security.

Immediate Steps to Take

Ensure monitoring for unusual traffic patterns, restrict subdomain access, and deploy network encryption to thwart ALPACA attacks.

Long-Term Security Practices

Regularly update TLS certificates, enhance network segmentation, and conduct security audits to mitigate ALPACA vulnerabilities.

Patching and Updates

Apply patches provided by vendors promptly, follow security advisories, and stay informed about emerging threats.