CVE-2023-20273: Cisco IOS XE Web UI RCE Vulnerability

CVE-2023-20273 Overview

A vulnerability in the web UI feature of Cisco IOS XE Software could allow an authenticated, remote attacker to inject commands with the privileges of root. This vulnerability is due to insufficient input validation. An attacker could exploit this vulnerability by sending crafted input to the web UI. A successful exploit could allow the attacker to inject commands to the underlying operating system with root privileges.

Critical Impact

This vulnerability has been added to CISA's Known Exploited Vulnerabilities (KEV) catalog due to confirmed active exploitation in the wild. Attackers with authenticated access to the web UI can achieve complete system compromise with root-level command execution capabilities on affected Cisco network devices.

Affected Products

• Cisco IOS XE Software (versions 16.1.1 through 17.12.1a)
• Cisco Catalyst 3650 Series Switches (all variants)
• Cisco Catalyst 3850 Series Switches (all variants)

Discovery Timeline

• October 25, 2023 - CVE-2023-20273 published to NVD
• October 28, 2025 - Last updated in NVD database

Technical Details for CVE-2023-20273

Vulnerability Analysis

This command injection vulnerability (CWE-78: Improper Neutralization of Special Elements used in an OS Command) resides in the web UI feature of Cisco IOS XE Software. The vulnerability enables authenticated attackers to execute arbitrary operating system commands with root privileges, effectively providing complete control over affected network infrastructure devices.

The vulnerability is particularly dangerous because it affects critical network infrastructure components—switches and routers that form the backbone of enterprise networks. Successful exploitation grants attackers the ability to modify device configurations, intercept network traffic, establish persistence, and pivot to other systems within the network.

This vulnerability is being actively exploited in the wild and has been added to CISA's Known Exploited Vulnerabilities catalog, underscoring the urgent need for organizations to apply mitigations immediately.

Root Cause

The root cause of CVE-2023-20273 is insufficient input validation in the web UI component of Cisco IOS XE Software. The web interface fails to properly sanitize user-supplied input before passing it to underlying operating system commands. This lack of proper input sanitization allows specially crafted requests to escape the intended command context and inject arbitrary commands that execute with root privileges.

Attack Vector

The attack requires network access to the device's web management interface and valid authentication credentials. Once authenticated, an attacker submits maliciously crafted input through the web UI that exploits the insufficient input validation. The injected commands execute at the operating system level with root privileges, allowing the attacker to:

• Execute arbitrary commands on the underlying operating system
• Modify device configurations
• Create new privileged accounts
• Install persistent backdoors
• Exfiltrate sensitive configuration data and credentials
• Pivot to attack other network devices and systems

The attack can be conducted remotely over the network, making any internet-exposed or internally accessible IOS XE web management interface a potential target. For technical exploitation details, refer to the Cisco Security Advisory.

Detection Methods for CVE-2023-20273

Indicators of Compromise

• Unexpected user accounts created on Cisco IOS XE devices, particularly accounts with privilege level 15
• Unusual configuration changes that were not authorized by network administrators
• Suspicious HTTP/HTTPS requests to the IOS XE web UI containing potential command injection patterns
• Anomalous process execution or shell commands observed on network devices
• Unexplained outbound network connections from Cisco devices to external IP addresses

Detection Strategies

• Monitor authentication logs for suspicious login attempts and successful authentications from unexpected sources
• Implement network-based detection rules to identify potential command injection payloads in HTTP/HTTPS traffic to IOS XE web interfaces
• Review device configurations regularly for unauthorized changes or new user accounts
• Deploy file integrity monitoring on device configurations to detect unauthorized modifications

Monitoring Recommendations

• Enable and centralize logging from all Cisco IOS XE devices to a SIEM platform for correlation analysis
• Configure alerts for administrative actions such as user creation, privilege changes, and configuration modifications
• Implement behavioral analysis to detect anomalous command patterns on network infrastructure
• Monitor for outbound connections from network devices, which may indicate command-and-control communication

How to Mitigate CVE-2023-20273

Immediate Actions Required

• Disable the HTTP/HTTPS server feature on affected devices if web-based management is not required using no ip http server and no ip http secure-server commands
• Restrict access to the web UI by implementing access control lists (ACLs) that limit management interface access to trusted IP addresses only
• Audit all Cisco IOS XE devices for signs of compromise, including unexpected user accounts or configuration changes
• Apply patches from Cisco immediately to all affected devices

Patch Information

Cisco has released security updates to address this vulnerability. Organizations should consult the Cisco Security Advisory for specific patched software versions and upgrade paths for their affected devices. Given the active exploitation of this vulnerability and its inclusion in the CISA KEV catalog, patching should be treated as an emergency priority.

Workarounds

• Disable the web UI feature entirely if not operationally required to eliminate the attack surface
• Implement strict network segmentation to isolate management interfaces from general network traffic
• Use out-of-band management networks for device administration rather than in-band web access
• Deploy intrusion prevention systems (IPS) with signatures capable of detecting command injection attempts

# Disable HTTP and HTTPS server on Cisco IOS XE
configure terminal
no ip http server
no ip http secure-server
exit
write memory

# If web UI is required, restrict access with ACL
ip access-list standard MGMT-ACCESS
 permit 10.0.0.0 0.0.0.255
 deny any log
exit
ip http access-class MGMT-ACCESS