CVE-2020-3227: Cisco IOS XE Auth Bypass Vulnerability

CVE-2020-3227 Overview

A critical authorization bypass vulnerability exists in the Cisco IOx application hosting infrastructure within Cisco IOS XE Software. This vulnerability allows an unauthenticated, remote attacker to execute Cisco IOx API commands without proper authorization. The flaw stems from incorrect handling of requests for authorization tokens, enabling attackers to craft malicious API calls that bypass authentication controls entirely.

Critical Impact

Unauthenticated remote attackers can obtain authorization tokens and execute arbitrary IOx API commands on affected Cisco IOS XE devices, potentially leading to complete device compromise.

Affected Products

• Cisco IOS XE versions 3.11.6e
• Cisco IOS XE versions 16.3.x through 16.12.x (including all maintenance releases)
• Cisco IOS XE devices with IOx application hosting infrastructure enabled

Discovery Timeline

• June 3, 2020 - CVE-2020-3227 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-3227

Vulnerability Analysis

This vulnerability represents a fundamental authorization bypass (CWE-863) in the Cisco IOx application hosting infrastructure. The IOx platform provides an application framework for hosting containerized applications on Cisco network devices. The vulnerability exists because the system incorrectly handles requests for authorization tokens, allowing unauthenticated users to obtain valid tokens without providing proper credentials.

The IOx API is designed to require authentication before processing requests. However, due to improper validation in the token generation mechanism, an attacker can craft specific API calls that circumvent the authorization checks. Once a valid token is obtained, the attacker gains the ability to execute any IOx API command on the affected device.

Root Cause

The root cause of CVE-2020-3227 is an authorization bypass vulnerability (CWE-863) combined with improper access control (CWE-264). The token request handler fails to properly validate whether the requestor has legitimate credentials before issuing an authorization token. This allows malicious actors to request and receive valid tokens that grant full API access without any form of authentication.

Attack Vector

The attack is conducted remotely over the network without requiring any user interaction or prior authentication. An attacker with network access to the IOx API endpoint can exploit this vulnerability by:

1. Identifying a vulnerable Cisco IOS XE device with IOx infrastructure exposed
2. Sending a crafted API request to the token endpoint
3. Receiving a valid authorization token in response
4. Using the obtained token to execute arbitrary IOx API commands

The vulnerability can be exploited against any accessible IOx API endpoint. Once successful, the attacker has full control over the IOx application environment, enabling deployment of malicious containers, access to sensitive configuration data, and potential lateral movement within the network infrastructure. See the Cisco Security Advisory for additional technical details.

Detection Methods for CVE-2020-3227

Indicators of Compromise

• Unexpected or unauthorized IOx API requests in device logs, particularly token generation requests from unknown sources
• Presence of unauthorized or unknown IOx applications deployed on affected devices
• Anomalous authentication patterns showing successful IOx API access without corresponding valid login events
• Unusual network traffic to IOx API endpoints from external or untrusted IP addresses

Detection Strategies

• Monitor IOx API access logs for token requests that do not correlate with legitimate administrative activity
• Implement network-based detection rules to identify crafted API calls targeting the IOx token endpoint
• Deploy SIEM correlation rules to alert on successful IOx API commands following failed or absent authentication attempts
• Conduct regular audits of deployed IOx applications to identify unauthorized container deployments

Monitoring Recommendations

• Enable verbose logging on all Cisco IOS XE devices with IOx infrastructure enabled
• Configure centralized log collection to capture and analyze IOx API activity across the network
• Implement network segmentation to restrict IOx API access to authorized management networks only
• Deploy behavioral analytics to baseline normal IOx API usage patterns and alert on deviations

How to Mitigate CVE-2020-3227

Immediate Actions Required

• Identify all Cisco IOS XE devices running affected versions (3.11.6e, 16.3.x through 16.12.x) with IOx infrastructure enabled
• Apply the security patches provided by Cisco immediately to all vulnerable devices
• Restrict network access to IOx API endpoints using access control lists (ACLs) to limit exposure
• Audit existing IOx deployments for signs of compromise or unauthorized applications

Patch Information

Cisco has released software updates that address this vulnerability. Administrators should consult the Cisco Security Advisory for specific fixed software versions applicable to their deployment. The advisory provides detailed information on which versions contain the security fix and guidance on the upgrade process.

Workarounds

• Disable IOx infrastructure on devices where application hosting functionality is not required using the no iox configuration command
• Implement strict ACLs to block external access to IOx API endpoints
• Use infrastructure firewalls to limit IOx API access to trusted management stations only
• If IOx cannot be disabled, place affected devices behind network segmentation that restricts API access

# Disable IOx infrastructure if not required
configure terminal
no iox
end
write memory

# Restrict API access via ACL
ip access-list extended IOX-RESTRICT
 permit tcp host <MANAGEMENT_IP> any eq 8443
 deny tcp any any eq 8443
 permit ip any any