CVE-2025-20265: Cisco Secure Firewall Management Center RCE

CVE-2025-20265 Overview

A critical command injection vulnerability exists in the RADIUS subsystem implementation of Cisco Secure Firewall Management Center (FMC) Software. This flaw allows an unauthenticated, remote attacker to inject arbitrary shell commands that are executed by the device with high-level privileges. The vulnerability stems from improper handling of user input during the RADIUS authentication phase, enabling attackers to craft malicious credentials that execute arbitrary commands when processed.

Critical Impact

This vulnerability allows unauthenticated remote attackers to achieve complete system compromise through command injection during RADIUS authentication, potentially leading to full control of the firewall management infrastructure.

Affected Products

• Cisco Secure Firewall Management Center version 7.0.7
• Cisco Secure Firewall Management Center version 7.7.0
• Cisco Secure FMC Software configured for RADIUS authentication (web-based management interface, SSH management, or both)

Discovery Timeline

• August 14, 2025 - CVE-2025-20265 published to NVD
• August 16, 2025 - Last updated in NVD database

Technical Details for CVE-2025-20265

Vulnerability Analysis

This vulnerability is classified as CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly known as an injection vulnerability. The flaw exists within the RADIUS subsystem of Cisco Secure Firewall Management Center and can be exploited remotely without authentication.

The vulnerability allows attackers to inject shell commands through the authentication phase, achieving command execution with elevated privileges on the target system. Since the attack vector is network-based with no user interaction required, the exploitation can be conducted against any exposed FMC instance configured for RADIUS authentication. The scope is changed, meaning a successful exploit can affect resources beyond the vulnerable component itself, potentially compromising connected security infrastructure.

Root Cause

The root cause of CVE-2025-20265 is inadequate input sanitization during the RADIUS authentication process. When user credentials are submitted for authentication against a configured RADIUS server, the FMC software fails to properly validate and sanitize the input before processing it in a shell context. This lack of input validation allows specially crafted characters and command sequences to escape the intended authentication context and execute as shell commands on the underlying system.

Attack Vector

An attacker can exploit this vulnerability by sending crafted input when entering credentials that will be authenticated at the configured RADIUS server. The attack requires:

1. The target Cisco Secure FMC must be configured for RADIUS authentication for the web-based management interface, SSH management, or both
2. Network access to the FMC management interface
3. Crafted credential input containing shell command injection payloads

When the malicious credentials are processed through the RADIUS authentication flow, the injected commands are executed with high privilege level on the FMC device, potentially allowing complete system compromise, configuration extraction, or lateral movement within the network.

The vulnerability mechanism involves the improper handling of special shell characters within authentication credential fields. When these fields are processed by the RADIUS subsystem, they are passed to shell execution contexts without proper escaping or sanitization. For detailed technical analysis, refer to the Cisco Security Advisory.

Detection Methods for CVE-2025-20265

Indicators of Compromise

• Unusual shell command execution logs originating from the RADIUS authentication process
• Authentication attempts containing special characters or shell metacharacters (;, |, $(), backticks)
• Unexpected process spawning from FMC authentication-related services
• Anomalous network connections initiated from the FMC management interface to external destinations

Detection Strategies

• Monitor authentication logs for unusual patterns in credential submissions, particularly those containing shell metacharacters
• Implement network detection rules to identify crafted RADIUS authentication attempts with injection payloads
• Review FMC system logs for unexpected command execution or privilege escalation events
• Deploy endpoint detection solutions capable of identifying command injection patterns and unauthorized shell activity

Monitoring Recommendations

• Enable comprehensive logging for RADIUS authentication events on Cisco Secure FMC
• Configure alerts for authentication failures with unusual payload characteristics
• Implement SIEM rules to correlate authentication anomalies with subsequent suspicious system activity
• Conduct regular audits of FMC configuration to identify instances where RADIUS authentication is enabled

How to Mitigate CVE-2025-20265

Immediate Actions Required

• Review Cisco Security Advisory cisco-sa-fmc-radius-rce-TNBKf79 for the latest patch information
• Identify all Cisco Secure FMC deployments configured for RADIUS authentication
• Apply vendor-provided security patches as soon as they become available
• Restrict network access to FMC management interfaces to trusted administrative networks only
• Monitor FMC systems for signs of exploitation while awaiting patch deployment

Patch Information

Cisco has released a security advisory addressing this vulnerability. Organizations should consult the Cisco Security Advisory for specific patch versions and upgrade guidance. Given the critical severity with a maximum CVSS score, immediate patching is strongly recommended for all affected FMC versions including 7.0.7 and 7.7.0.

Workarounds

• Temporarily disable RADIUS authentication for FMC web-based management and SSH management interfaces if operationally feasible
• Implement strict network segmentation to limit access to FMC management interfaces from untrusted networks
• Use alternative authentication mechanisms (such as local authentication) until patches can be applied
• Deploy network-based intrusion detection/prevention systems with rules to identify command injection attempts

# Example: Restrict FMC management access via ACL (adjust to your environment)
# Apply to firewall protecting FMC management interface
access-list FMC-MGMT-RESTRICT extended permit tcp host 10.0.1.0/24 host <FMC_IP> eq 443
access-list FMC-MGMT-RESTRICT extended permit tcp host 10.0.1.0/24 host <FMC_IP> eq 22
access-list FMC-MGMT-RESTRICT extended deny tcp any host <FMC_IP> eq 443
access-list FMC-MGMT-RESTRICT extended deny tcp any host <FMC_IP> eq 22