Vulnerability Overview (At a Glance)

• CVE ID: CVE-2025-62877
• Product: SUSE Virtualization (Harvester)
• Affected Versions: Interactive Installer 1.5.x and 1.6.x
• Vulnerability Type: Default credential exposure / insecure installation flow
• CVSS v3 Score: 9.8 (Critical)
• Severity: Critical
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Exploitability: High
• Exploit Availability: No public exploit kit, but exploitation is trivial
• Patch Status: Fixed in Harvester installer version 1.7.0 and later

What Is the Issue?

CVE-2025-62877 is a critical security flaw in the interactive installer used by SUSE Virtualization (Harvester). During installation or node expansion, the installer brings up network connectivity before forcing a reset of the operating system’s default SSH password.

This creates a short but dangerous window where:

• SSH is reachable over the network
• A default OS login password is still valid
• No authentication hardening has occurred yet

Any attacker with network access at that moment can log in remotely using the default SSH credentials and gain full system access.

This is not a cryptographic weakness or a bug in SSH itself. It is a process ordering flaw in the installer workflow.

Why This Is Dangerous

Even though the exposure window is short, the impact is severe:

• Attackers gain direct shell access to a node
• Commands can be executed with administrative privileges
• Malware, backdoors, or persistence mechanisms can be installed
• Cluster integrity can be compromised before it even goes live
• Lateral movement to other systems becomes possible

Because the attacker does not need credentials, interaction, or prior access, the vulnerability scores near the maximum on the CVSS scale.

Who Is Affected

Systems are vulnerable if all of the following are true:

• Harvester interactive installer is used
• Installer version is 1.5.x or 1.6.x
• The installer is used to:
  • Create a new cluster, or
  • Add a node to an existing cluster
• The system is reachable over a network during installation

Not Affected

• Installations using PXE boot with a predefined configuration
• Systems where SSH access is blocked during installation
• Environments already running installer v1.7.0 or newer

How an Attacker Exploits This

Attack Flow

1. Administrator starts the interactive Harvester installer
2. Installer enables networking early in the process
3. Default SSH password is still active
4. Attacker scans the network for SSH
5. Attacker logs in using default credentials
6. Full system access is obtained

This attack does not require brute force, malware, or advanced tooling. A standard SSH client is sufficient.

Proof of Concept (PoC) Status

• No official exploit code has been released publicly
• No specialized payload is required
• A basic SSH login attempt during the installation window acts as a functional proof of concept
• Exploitation can be easily automated by monitoring for newly active SSH services

Because default credentials are involved, exploit development effort is minimal.

Detection and Monitoring Guidance

Key Detection Indicators

• Successful SSH logins occurring during installation timeframes
• SSH access before the installer completes password hardening
• Shell activity before cluster initialization finishes
• Unexpected administrative sessions during node provisioning

Recommended Log Sources

Example Detection Rule

Alert when:
  SSH login succeeds
AND
  System installation state = "in progress"
AND
  Password reset event not yet completed

This rule works well in SIEM platforms that support event correlation and time-based logic.

MITRE ATT&CK Mapping

• T1078 – Valid Accounts
  Exploitation relies on default system credentials.
• T1133 – External Remote Services
  Unauthorized access is gained through exposed SSH services.

Mitigation and Remediation

Official Fix (Recommended)

Upgrade to Harvester Interactive Installer version 1.7.0 or later.
This version ensures that:

• Default passwords are reset before networking is enabled
• SSH is not exposed during insecure installation phases

Official Patch Link:
Use the official Harvester installer releases provided by SUSE for version 1.7.0+

Temporary Mitigations (If Upgrade Is Delayed)

• Block inbound SSH (port 22) during installation
• Use isolated VLANs or air-gapped networks for provisioning
• Prefer PXE installations with predefined secure credentials
• Monitor installation windows closely for unexpected access

Final Takeaway

CVE-2025-62877 is a classic example of how default credentials combined with timing issues can lead to critical compromise. Even brief exposure during installation is enough for a full system takeover.

If you are using Harvester and have ever installed or expanded clusters using the interactive installer, verify installer versions immediately and ensure vulnerable versions are no longer in use.