CVE-2025-20158 in Session Initiation Protocol Software
Summary
by MITRE • 02/19/2025
A vulnerability in the debug shell of Cisco Video Phone 8875 and Cisco Desk Phone 9800 Series could allow an authenticated, local attacker to access sensitive information on an affected device. To exploit this vulnerability, the attacker must have valid administrative credentials with SSH access on the affected device. SSH access is disabled by default.
This vulnerability is due to insufficient validation of user-supplied input by the debug shell of an affected device. An attacker could exploit this vulnerability by sending a crafted SSH client command to the CLI. A successful exploit could allow the attacker to access sensitive information on the underlying operating system.
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Analysis
by VulDB Data Team • 12/15/2025
The vulnerability identified as CVE-2025-20158 represents a critical security flaw within the debug shell functionality of Cisco Video Phone 8875 and Cisco Desk Phone 9800 Series devices. This issue stems from inadequate input validation mechanisms within the debug shell component that processes commands issued through the command line interface. The vulnerability specifically affects devices where SSH access has been enabled and administrative credentials have been properly configured, as the exploit requires authenticated access to leverage the flaw. The default security configuration of these devices disables SSH access, which serves as an initial protective measure against unauthorized exploitation attempts.
The technical implementation of this vulnerability manifests through insufficient sanitization of user-supplied input within the debug shell environment. When an authenticated administrator establishes SSH access to the device, the debug shell component fails to properly validate or sanitize commands received from the SSH client interface. This input validation failure creates a pathway for attackers to craft specific SSH client commands that can bypass normal security restrictions. The vulnerability operates at the command execution level where malicious input can potentially escalate privileges or access underlying system components that should remain restricted to authorized personnel only.
From an operational perspective, the impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attack vectors. An attacker who successfully exploits this vulnerability could gain access to sensitive system information including configuration files, user credentials, network settings, and potentially other system-level data that resides within the operating system's memory or storage. The debug shell environment typically provides elevated access to system resources, making this vulnerability particularly dangerous as it could allow for privilege escalation or lateral movement within a network environment. This vulnerability directly aligns with CWE-20, which describes improper input validation, and represents a classic example of how inadequate sanitization can create security breaches.
The exploitation of this vulnerability requires a specific attack vector that involves an authenticated administrative session through SSH, which provides multiple layers of defense in the default configuration. However, when SSH access is enabled and valid administrative credentials are available, the attack surface expands significantly. The vulnerability demonstrates how default security configurations can provide effective protection, but also highlights the importance of proper access control management. Organizations should consider implementing additional security controls such as multi-factor authentication, network segmentation, and regular access reviews to minimize the risk associated with this type of vulnerability.
Mitigation strategies for CVE-2025-20158 should prioritize maintaining the default security posture of disabling SSH access unless explicitly required for operational purposes. When SSH access is necessary, organizations should implement strict access controls including the use of dedicated administrative accounts, regular credential rotation, and monitoring of SSH sessions. Network-based controls such as firewall rules that restrict SSH access to specific administrative workstations can provide additional protection layers. The implementation of security monitoring solutions that can detect anomalous command sequences or unusual access patterns in the debug shell environment would enhance detection capabilities. According to ATT&CK framework, this vulnerability could be categorized under T1059.005 for command and scripting interpreter, and T1566 for credential access, highlighting the need for comprehensive defensive measures that address both the technical flaw and operational security considerations. Regular security assessments and vulnerability scanning should include verification of SSH access status and proper input validation mechanisms within device management interfaces.