CVE-2022-20693: Cisco IOS XE Web UI RCE Vulnerability

CVE-2022-20693 Overview

A command injection vulnerability exists in the web UI feature of Cisco IOS XE Software that could allow an authenticated, remote attacker to perform an injection attack against an affected device. This vulnerability stems from insufficient input validation in the web UI API, enabling attackers to inject commands to the underlying operating system with root privileges. Organizations running affected versions of Cisco IOS XE Software should prioritize patching this vulnerability due to the potential for complete device compromise.

Critical Impact

Successful exploitation allows authenticated attackers to execute arbitrary commands with root privileges on the underlying operating system, potentially leading to complete device compromise, network infrastructure takeover, and lateral movement within the enterprise environment.

Affected Products

• Cisco IOS XE versions 3.15.1xbs and 3.15.2xbs
• Cisco IOS XE versions 16.12.1 through 16.12.6a (including all sub-releases)
• Cisco IOS XE versions 17.1.1 through 17.6.1w (including all sub-releases)

Discovery Timeline

• April 15, 2022 - CVE-2022-20693 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-20693

Vulnerability Analysis

This vulnerability is classified under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component) and CWE-78 (Improper Neutralization of Special Elements used in an OS Command). The web UI API in Cisco IOS XE Software fails to properly sanitize user-supplied input before processing it in system commands. When an authenticated attacker sends specially crafted input to the web UI API, the malicious payload bypasses input validation controls and gets executed in the context of the underlying operating system.

The attack requires authentication, meaning the attacker must possess valid credentials to access the web UI. However, once authenticated, the attacker can leverage this vulnerability to escalate privileges to root level, gaining complete control over the affected network device. This represents a significant risk in environments where multiple administrators have web UI access or where credential theft is possible.

Root Cause

The root cause of this vulnerability is insufficient input validation within the web UI API component of Cisco IOS XE Software. The application fails to properly sanitize special characters and command separators in user input before passing it to system functions that execute operating system commands. This allows attackers to inject additional commands that are then executed with elevated privileges.

Attack Vector

The attack is conducted remotely over the network and requires the attacker to be authenticated to the web UI. The attacker crafts malicious input containing operating system command injection payloads and submits it through the web UI API. Due to the lack of proper input sanitization, these injected commands are executed by the underlying Linux-based operating system with root privileges.

The vulnerability exploitation involves sending crafted HTTP requests to the web UI API endpoints. Attackers may inject shell metacharacters such as semicolons, pipes, or command substitution syntax to chain arbitrary commands to legitimate operations. Since the web UI process runs with elevated privileges, any injected commands inherit root access.

Detection Methods for CVE-2022-20693

Indicators of Compromise

• Unusual HTTP requests to the IOS XE web UI API containing shell metacharacters (;, |, $(), backticks)
• Unexpected processes spawned by the web UI service with root privileges
• Anomalous system command execution patterns on IOS XE devices following web UI authentication events
• Log entries showing authentication followed by administrative commands not typically associated with that user

Detection Strategies

• Monitor web UI access logs for requests containing potential command injection patterns such as shell metacharacters
• Implement network-based intrusion detection rules to identify crafted payloads targeting the IOS XE web UI API
• Review system logs on Cisco IOS XE devices for unexpected command execution or process creation following web management activity
• Deploy endpoint detection on network management stations to identify potential attacker activity targeting infrastructure devices

Monitoring Recommendations

• Enable and centralize logging for all Cisco IOS XE web UI access attempts and API interactions
• Configure alerting for failed authentication attempts followed by successful logins to the web UI
• Monitor for configuration changes or new user account creation on IOS XE devices outside of change windows
• Implement behavioral analysis to detect anomalous administrative actions that deviate from established baselines

How to Mitigate CVE-2022-20693

Immediate Actions Required

• Review the Cisco Security Advisory and apply the recommended software updates
• Restrict web UI access to trusted management networks and IP addresses only
• Audit and minimize the number of accounts with web UI administrative access
• Enable multi-factor authentication where supported to reduce credential-based attack risk

Patch Information

Cisco has released security updates to address this vulnerability. Organizations should consult the Cisco Security Advisory cisco-sa-webuiapi-inj-Nyrq92Od for specific fixed software versions and upgrade guidance. The advisory provides detailed information about affected releases and the corresponding patched versions.

Affected versions span multiple release trains including:

• 3.15.x releases
• 16.12.x releases
• 17.1.x through 17.6.x releases

Administrators should upgrade to the latest available fixed release within their deployment's supported software train.

Workarounds

• Disable the web UI feature if it is not required for device management operations
• Implement strict access control lists (ACLs) to limit web UI access to dedicated management networks
• Use SSH and CLI-based management as an alternative to the web UI until patching is complete
• Deploy a web application firewall (WAF) or reverse proxy with input filtering capabilities in front of the management interface

# Disable HTTP/HTTPS server on Cisco IOS XE (if web UI not required)
configure terminal
no ip http server
no ip http secure-server
end
write memory

# Restrict web UI access to management subnet only
configure terminal
ip http access-class 10
access-list 10 permit 10.0.0.0 0.0.0.255
access-list 10 deny any
end
write memory