CVE-2020-15312 in CloudCNM SecuManager
Summary
by MITRE
Zyxel CloudCNM SecuManager 3.1.0 and 3.1.1 has a hardcoded DSA SSH key for the root account.
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Analysis
by VulDB Data Team • 06/30/2020
The vulnerability identified as CVE-2020-15312 affects Zyxel CloudCNM SecuManager versions 3.1.0 and 3.1.1, representing a critical security flaw that compromises the integrity of the affected system. This issue manifests through the presence of a hardcoded DSA SSH key within the root account configuration, creating a persistent backdoor access mechanism that undermines the fundamental security assumptions of the device.
The technical implementation of this vulnerability involves the inclusion of a well-known DSA private key within the firmware of the SecuManager appliance. This hardcoded key allows any attacker who possesses the corresponding public key to establish unauthorized SSH sessions as the root user without requiring legitimate credentials. The flaw exists at the authentication layer where the system relies on a static cryptographic key rather than dynamic credential generation, violating security best practices for access control mechanisms. The DSA algorithm, while cryptographically sound when properly implemented, becomes ineffective when the private key component is embedded within the software and distributed across multiple installations.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it provides attackers with complete administrative control over the affected system. Once exploited, adversaries can manipulate network configurations, modify security policies, access sensitive data, and potentially use the compromised device as a pivot point for lateral movement within the network infrastructure. The persistence of this backdoor means that even after system reboots or firmware updates, the vulnerability remains exploitable unless the hardcoded key is explicitly removed from the system configuration. This characteristic aligns with attack patterns documented in the MITRE ATT&CK framework under the T1078 technique for valid accounts and T1566 for credential harvesting, as the vulnerability enables unauthorized access through legitimate authentication mechanisms.
Organizations utilizing affected Zyxel CloudCNM SecuManager appliances face significant risk exposure due to the widespread nature of this vulnerability. The hardcoded nature of the key means that any entity with access to the public key can exploit the system, potentially including malicious actors who may have obtained the key through various means such as public repositories or security research publications. The vulnerability directly relates to CWE-798, which addresses the use of hardcoded credentials, and CWE-310, covering cryptographic issues in authentication mechanisms. Security teams must consider implementing network segmentation, monitoring for unauthorized SSH access attempts, and conducting comprehensive inventory audits to identify all affected devices within their infrastructure. The remediation process requires immediate firmware updates from Zyxel, though organizations should also consider implementing additional security controls such as SSH key management policies, network access controls, and continuous monitoring of system access logs to detect potential exploitation attempts.