CVE-2025-71261: Harvester's SUSE Virtualization Registration Client Vulnerable to MITM and DOS

A vulnerability has been identified in the SUSE Virtualization (Harvester) Rancher integration mechanism where by default the registration client uses an insecure TLS option that fails to verify the remote server’s certificate. This security gap could allow the execution of a man-in-the-middle (MitM) attack against SUSE Virtualization.

An attacker with network-level access between the SUSE Virtualization and Rancher Manager could interfere with the TLS handshake and abuse it to bypass TLS as a security control. The registration client could be misled to send cluster registration requests to an impersonated remote service. Additionally, because the system processes response payloads without performing size validation, an attacker could induce a memory buffer overflow, leading to a potential crash of the SUSE Virtualization registration controller.

Note that this vulnerability only affects the cluster registration configuration (the cluster-registration-url setting) which is distinct from the secured configuration used to maintain operational connectivity between SUSE Virtualization and Rancher Manager, as well as between the manager and hosted downstream clusters.

Please consult the associated MITRE ATT&CK - Technique - Adversary-in-the-Middle and MITRE ATT&CK - Technique - Endpoint Denial of Service: Application or System Exploitation for further information about this category of attack.