Overview
The cybersecurity landscape is constantly evolving, and a new vulnerability has surfaced, one that affects the TACACS+ protocol in Cisco’s IOS Software and IOS XE Software. This vulnerability, identified as CVE-2025-20160, is critical as it allows an unauthenticated, remote attacker to potentially view sensitive data or bypass the authentication process. This vulnerability matters because it presents a significant security risk to any organization using the affected Cisco software. If exploited, attackers could gain unauthorized access to sensitive data and systems, leading to potential system compromise or data leakage.
Vulnerability Summary
CVE ID: CVE-2025-20160
Severity: High (CVSS: 8.1)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Unauthorized access to sensitive information in a TACACS+ message, bypassing authentication and potentially gaining access to the affected device.
Affected Products
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Product | Affected Versions
Cisco IOS Software | All versions prior to the latest patch
Cisco IOS XE Software | All versions prior to the latest patch
How the Exploit Works
This vulnerability stems from a flaw in the implementation of the TACACS+ protocol in Cisco IOS and IOS XE Software. The system does not properly check whether the required TACACS+ shared secret is configured. An unauthenticated, remote attacker can exploit this vulnerability by positioning themselves as a ‘man-in-the-middle’. They can intercept and read unencrypted TACACS+ messages or impersonate the TACACS+ server, falsely accepting arbitrary authentication requests. A successful exploit could allow the attacker to view sensitive information in a TACACS+ message or bypass authentication, gaining unauthorized access to the affected device.
Conceptual Example Code
The following pseudocode represents a conceptual example of how an attacker might exploit this vulnerability:
def exploit(target_ip):
# Pretend to be the TACACS+ server
tacacs_server = TacacsPlusServer()
# Intercept the request
request = tacacs_server.intercept_request(target_ip)
# Return a successful authentication response regardless of the original request
response = tacacs_server.create_response(request, authenticated=True)
# Send the response back to the client
tacacs_server.send_response(target_ip, response)In this example, the attacker creates a fake TACACS+ server, intercepts the authentication request, and sends back a response indicating successful authentication, regardless of the actual request content.
