CVE-2023-20048: Cisco Secure Firewall Auth Bypass Flaw

CVE-2023-20048 Overview

A critical authorization bypass vulnerability exists in the web services interface of Cisco Firepower Management Center (FMC) Software that could allow an authenticated, remote attacker to execute unauthorized configuration commands on Firepower Threat Defense (FTD) devices managed by the FMC Software. This vulnerability stems from insufficient authorization of configuration commands sent through the web service interface, enabling attackers with valid credentials to manipulate device configurations beyond their intended privileges.

Critical Impact

Authenticated attackers can execute unauthorized configuration commands on FTD devices, potentially compromising network security policies, firewall rules, and overall security posture of the managed infrastructure.

Affected Products

• Cisco Secure Firewall Management Center (multiple versions)
• Firepower Threat Defense (FTD) devices managed by affected FMC versions

Discovery Timeline

• November 1, 2023 - CVE-2023-20048 published to NVD
• November 26, 2024 - Last updated in NVD database

Technical Details for CVE-2023-20048

Vulnerability Analysis

This vulnerability affects the web services interface of Cisco Firepower Management Center Software. The core issue lies in the insufficient authorization controls applied to configuration commands processed through the web service interface. When an authenticated user sends specially crafted HTTP requests to the FMC, the system fails to properly validate whether the user has the appropriate permissions to execute the requested configuration changes on managed FTD devices.

The vulnerability is classified under CWE-269 (Improper Privilege Management) and CWE-863 (Incorrect Authorization), both of which relate to inadequate access control mechanisms. The scope-changing nature of this vulnerability means that a successful exploit on the FMC can affect the security of other components—specifically, the FTD devices under its management.

Root Cause

The root cause of CVE-2023-20048 is the insufficient authorization validation in the web services interface of the Cisco FMC Software. The application fails to properly verify that authenticated users have the necessary privileges to execute specific configuration commands before processing those requests. This authorization gap allows users with valid but potentially limited credentials to perform actions beyond their intended access level.

Attack Vector

The attack vector is network-based and requires authentication to the FMC web services interface. An attacker would need to:

1. Obtain valid credentials for the Cisco FMC Software (either through compromise, social engineering, or insider access)
2. Authenticate to the FMC web services interface
3. Craft and send malicious HTTP requests containing unauthorized configuration commands
4. The FMC processes these commands without proper authorization checks and executes them on the targeted FTD device

The vulnerability allows configuration changes to be pushed to FTD devices managed by the FMC, potentially altering firewall rules, security policies, or other critical security configurations. For detailed technical information, refer to the Cisco Security Advisory.

Detection Methods for CVE-2023-20048

Indicators of Compromise

• Unexpected configuration changes on FTD devices not initiated by authorized administrators
• Anomalous HTTP requests to the FMC web services interface from authenticated sessions
• Unauthorized modification of firewall rules, access policies, or security configurations
• Audit logs showing configuration commands executed by users without appropriate privileges

Detection Strategies

• Monitor FMC audit logs for configuration changes and correlate with authorized change management tickets
• Implement behavioral analysis on authenticated sessions to detect unusual command patterns
• Deploy network detection rules to identify crafted HTTP requests targeting the FMC web services interface
• Review user activity logs for privilege escalation patterns or unauthorized configuration attempts

Monitoring Recommendations

• Enable comprehensive logging on all Cisco FMC instances and centralize log collection
• Configure alerts for any configuration changes to managed FTD devices
• Implement SIEM rules to correlate FMC authentication events with subsequent configuration commands
• Regularly audit user permissions and access levels within the FMC environment

How to Mitigate CVE-2023-20048

Immediate Actions Required

• Apply the security patches provided by Cisco immediately to all affected FMC installations
• Review and restrict user accounts with access to the FMC web services interface
• Audit recent configuration changes on all managed FTD devices for unauthorized modifications
• Implement network segmentation to limit access to the FMC management interface

Patch Information

Cisco has released security updates to address this vulnerability. Organizations should consult the Cisco Security Advisory for specific version information and upgrade paths. The advisory provides detailed guidance on affected versions and the corresponding fixed releases.

Workarounds

• Restrict access to the FMC web services interface to trusted networks and IP addresses only
• Implement multi-factor authentication for all FMC administrative access
• Apply the principle of least privilege when assigning user roles within the FMC
• Monitor and log all API and web services interface activity for security review

# Example: Restrict FMC management access to specific trusted networks
# Configure access control on network devices upstream of FMC
# Consult Cisco documentation for FMC-specific access restrictions
access-list FMC-MGMT-ACL permit tcp 10.0.0.0/24 host 192.168.1.100 eq 443
access-list FMC-MGMT-ACL deny ip any host 192.168.1.100