CVE-2024-20356: Cisco IMC Privilege Escalation Flaw

CVE-2024-20356 Overview

CVE-2024-20356 is a command injection vulnerability in the web-based management interface of Cisco Integrated Management Controller (IMC). This vulnerability allows an authenticated, remote attacker with Administrator-level privileges to perform command injection attacks on affected systems and elevate their privileges to root. The vulnerability stems from insufficient user input validation in the web-based management interface.

Critical Impact

Attackers with administrative access can exploit this command injection flaw to gain root-level privileges on affected Cisco IMC systems, potentially compromising the entire server infrastructure managed by the IMC.

Affected Products

• Cisco Integrated Management Controller (IMC)
• Cisco UCS C-Series Rack Servers (utilizing IMC)
• Cisco UCS S-Series Storage Servers (utilizing IMC)

Discovery Timeline

• April 24, 2024 - CVE-2024-20356 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2024-20356

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The flaw exists within the web-based management interface of Cisco IMC, which provides out-of-band management capabilities for Cisco server hardware.

The attack requires network access and valid Administrator-level credentials to the IMC web interface. While the prerequisite of administrator privileges limits the initial attack surface, successful exploitation results in root-level access to the underlying operating system. This represents a vertical privilege escalation from application administrator to full system control, with scope change implications that could affect other components managed by the compromised IMC.

Root Cause

The root cause of this vulnerability is insufficient user input validation in the web-based management interface. When processing certain administrative commands through the web interface, the application fails to properly sanitize user-supplied input before passing it to underlying operating system commands. This allows specially crafted input containing shell metacharacters or command separators to be executed with elevated privileges.

Attack Vector

The attack is conducted remotely over the network by an authenticated attacker with Administrator-level privileges to the Cisco IMC web interface. The attacker crafts malicious input containing injected commands and submits it through the web-based management interface.

The vulnerability allows the attacker to bypass the normal privilege boundaries of the web application and execute arbitrary commands at the root level on the underlying operating system. This can lead to complete compromise of the server management infrastructure, including potential access to host system credentials, modification of firmware settings, and lateral movement to managed servers.

The attack flow involves:

1. Authenticating to the Cisco IMC web interface with Administrator credentials
2. Identifying vulnerable input fields or API endpoints that process commands
3. Crafting payloads that include command injection sequences
4. Submitting the malicious input through the web interface
5. Achieving code execution with root privileges on the IMC system

For detailed technical information about this vulnerability, refer to the Cisco Security Advisory.

Detection Methods for CVE-2024-20356

Indicators of Compromise

• Unexpected command execution patterns in IMC system logs
• Anomalous administrative sessions or login activity from unusual IP addresses
• Evidence of shell command syntax or metacharacters in web application logs
• Unauthorized changes to system configurations or firmware settings
• Creation of unexpected user accounts or modification of existing credentials

Detection Strategies

• Monitor Cisco IMC web interface logs for unusual command patterns or suspicious input strings
• Implement network-based intrusion detection rules to identify command injection payload patterns in HTTP traffic to IMC interfaces
• Deploy SIEM correlation rules to detect privilege escalation sequences following administrative authentication
• Review authentication logs for brute-force attempts or credential stuffing targeting IMC administrator accounts

Monitoring Recommendations

• Enable comprehensive audit logging on all Cisco IMC instances
• Configure alerts for administrative actions performed outside of normal maintenance windows
• Monitor network traffic to IMC management interfaces for anomalous patterns
• Implement file integrity monitoring on critical IMC system files to detect unauthorized modifications

How to Mitigate CVE-2024-20356

Immediate Actions Required

• Apply the security patch from Cisco immediately on all affected IMC deployments
• Restrict network access to IMC management interfaces using firewall rules and access control lists
• Audit and review all accounts with Administrator-level privileges to the IMC web interface
• Implement multi-factor authentication for administrative access where supported
• Monitor systems for indicators of compromise while patches are being deployed

Patch Information

Cisco has released a security update addressing this vulnerability. Administrators should consult the Cisco Security Advisory for specific patch versions and upgrade instructions applicable to their deployment. Organizations should prioritize patching based on the exposure of their IMC management interfaces and follow Cisco's recommended upgrade path.

Workarounds

• Restrict access to the IMC web-based management interface to trusted networks only using network segmentation and ACLs
• Implement jump hosts or bastion servers for administrative access to reduce the attack surface
• Disable unused administrative interfaces and services on IMC deployments
• Enforce strict password policies and regularly rotate Administrator credentials

# Example: Restrict IMC management interface access using firewall rules
# Allow access only from trusted management network
iptables -A INPUT -p tcp --dport 443 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP