Information Leakage / Subdomain Enumeration
Subdomain enumeration is a type of Information Leakage vulnerability (CWE-200) which occurs when a malicious actor is able to enumerate subdomains of a target domain, often without authorization. Subdomain enumeration is an infrastructure vulnerability which can be used to reveal information about the target's network infrastructure and attack surface. Information such as the target's IP address, ports, services, and other resources can be exposed. This can be done by using various tools such as DNS enumeration, brute-forcing, or scanning. According to the OWASP Testing Guide, subdomain enumeration is a passive attack which can be used to gain information about the target's infrastructure.
Subdomain enumeration can lead to serious security issues such as information leakage, data breaches, and network compromise. By enumerating subdomains, an attacker can gain access to confidential information or data, such as usernames and passwords, that can be used to launch further attacks. An attacker can also use enumerated subdomains to gain access to sensitive applications or systems. This can lead to a compromise of the entire network.
The best way to prevent subdomain enumeration is to implement proper access controls. Restricting access to subdomains and preventing unauthorized users from accessing them is the most effective way to protect against this vulnerability. It is also important to ensure that all subdomains are properly configured and secured. Additionally, organizations should implement regular vulnerability scans to detect subdomain enumeration attempts.