CVE-2024-20284: Cisco NX-OS Privilege Escalation Flaw

CVE-2024-20284 Overview

A vulnerability in the Python interpreter of Cisco NX-OS Software could allow an authenticated, low-privileged, local attacker to escape the Python sandbox and gain unauthorized access to the underlying operating system of the device. This sandbox escape vulnerability enables attackers to break out of the restricted Python execution environment and execute arbitrary commands on the underlying operating system with the privileges of the authenticated user.

Critical Impact

Authenticated attackers with Python execution privileges can escape the sandbox environment to execute arbitrary commands on the underlying operating system, potentially compromising the integrity and security of network infrastructure devices.

Affected Products

• Cisco NX-OS Software
• Cisco Nexus 3000 Series Switches
• Cisco Nexus 9000 Series Switches (Standalone NX-OS Mode)

Discovery Timeline

• August 28, 2024 - CVE-2024-20284 published to NVD
• October 17, 2024 - Last updated in NVD database

Technical Details for CVE-2024-20284

Vulnerability Analysis

This vulnerability represents a sandbox escape flaw in the Python interpreter implementation within Cisco NX-OS Software. The Python sandbox in NX-OS is designed to provide a restricted execution environment that prevents users from directly accessing the underlying Linux operating system. However, due to insufficient validation of user-supplied input, an authenticated attacker can manipulate specific functions within the Python interpreter to break out of this sandboxed environment.

The attack requires local access and authentication with Python execution privileges. Once the sandbox is escaped, the attacker gains the ability to execute arbitrary commands on the underlying operating system with the same privileges as the authenticated user. This can lead to unauthorized access to sensitive system configurations, potential lateral movement within the network infrastructure, and compromise of device integrity.

Root Cause

The vulnerability stems from insufficient validation of user-supplied input within the Python interpreter's sandbox implementation. The NX-OS Python sandbox is intended to restrict what operations users can perform, but certain functions do not properly validate or sanitize input before processing, allowing attackers to manipulate these functions to escape the restricted environment.

Attack Vector

The attack is executed locally by an authenticated user who has been granted Python execution privileges on the affected device. The attacker leverages the insufficient input validation by manipulating specific Python functions to break out of the sandbox constraints. Once outside the sandbox, the attacker can execute arbitrary commands on the underlying Linux operating system.

The exploitation process involves:

1. Authenticating to the NX-OS device with valid credentials that include Python execution privileges
2. Accessing the Python interpreter shell on the device
3. Manipulating specific functions within the interpreter that lack proper input validation
4. Escaping the sandbox environment to access the underlying operating system
5. Executing arbitrary commands with the privileges of the authenticated user

For detailed information on Python execution privileges and configuration, see the Cisco NX-OS Programmability Guide.

Detection Methods for CVE-2024-20284

Indicators of Compromise

• Unusual Python interpreter activity or unexpected process spawning from Python sessions on NX-OS devices
• Commands executed on the underlying Linux OS that originate from Python interpreter sessions
• Unexpected file system access or modifications outside the normal Python sandbox scope
• Anomalous user activity patterns from accounts with Python execution privileges

Detection Strategies

• Monitor NX-OS system logs for unusual Python interpreter activity and command execution patterns
• Implement logging and alerting for shell commands executed outside the Python sandbox environment
• Review authentication logs for accounts with Python execution privileges accessing the Python shell
• Deploy network behavior analysis to detect unusual activity from network infrastructure devices

Monitoring Recommendations

• Enable comprehensive logging for all Python interpreter sessions on affected NX-OS devices
• Configure syslog forwarding to centralized SIEM solutions for correlation and analysis
• Establish baseline behavior patterns for Python usage and alert on deviations
• Regularly audit user accounts with Python execution privileges and remove unnecessary access

How to Mitigate CVE-2024-20284

Immediate Actions Required

• Review and apply security patches from Cisco as outlined in the Cisco Security Advisory
• Audit all user accounts to identify those with Python execution privileges and remove access where not required
• Implement the principle of least privilege for all network device access
• Monitor affected devices for signs of exploitation while patching is in progress

Patch Information

Cisco has released security updates to address this vulnerability. Administrators should consult the Cisco Security Advisory cisco-sa-nxos-psbe-ce-YvbTn5du for specific fixed software versions and upgrade instructions for their affected devices. The advisory provides detailed information about which NX-OS versions are vulnerable and the recommended upgrade paths.

Workarounds

• Restrict Python execution privileges to only essential personnel and applications that require programmatic access
• Implement strict access control lists (ACLs) and role-based access control (RBAC) on affected devices
• Consider disabling Python interpreter access on devices where it is not operationally required
• Implement network segmentation to limit the impact of potential device compromise

# Example: Review users with Python execution privileges
show run | include "role name\|username"

# Example: Restrict Python access by modifying user roles
configure terminal
role name limited-user
  rule 1 deny command python
  rule 2 deny command python3
end