This error message typically appears when a web browser attempts to establish a secure connection with a server, but the server’s certificate doesn’t contain a valid name matching the address used to access it. For instance, attempting to reach a server using the address “example.net” when the certificate is only valid for “www.example.net” can trigger this problem. This mismatch prevents the browser from verifying the server’s identity, protecting users from potential security risks like man-in-the-middle attacks where a malicious actor intercepts communication.
Secure communication relies on the principle of trust. Browsers use certificates to confirm that they are communicating with the intended server. When the intended server name is absent from the certificate’s designated fields, this trust cannot be established. Historically, reliance on exact hostname matches emerged as the primary security measure. However, the evolution of the internet and diverse naming conventions necessitated alternative methods of verification like Subject Alternative Names (SANs) in certificates, enabling a single certificate to cover multiple domains and subdomains. This enhancement significantly strengthens security by providing more granular control over which names are considered valid for a particular certificate. The absence of proper matching highlights the importance of meticulous certificate management for maintaining a secure online environment.
