Critical OpenSSH Vulnerabilities Expose Millions of Servers to Man-in-the-Middle and Denial-of-Service Attacks

Two new vulnerabilities in OpenSSH, CVE-2025-26465 and CVE-2025-26466, pose a significant threat to millions of internet-exposed servers. These flaws could allow attackers to execute man-in-the-middle (MitM) attacks or launch denial-of-service (DoS) attacks, potentially compromising sensitive data and disrupting services.

The first vulnerability, CVE-2025-26465, affects OpenSSH clients when the 'VerifyHostKeyDNS' option is enabled. The second, CVE-2025-26466, is exploitable regardless of this setting. An attacker can exploit these vulnerabilities without user interaction, even in the absence of SSHFP records.

With approximately 33 million servers worldwide running OpenSSH, the potential impact is substantial. Successful exploitation could lead to the interception and manipulation of data, as well as DoS attacks that consume server resources. Users are urged to review security advisories and implement recommended mitigations to protect their systems.