CVE-2024-20437: Cisco IOS XE CSRF Vulnerability

CVE-2024-20437 Overview

A cross-site request forgery (CSRF) vulnerability exists in the web-based management interface of Cisco IOS XE Software that could allow an unauthenticated, remote attacker to execute commands on the command-line interface (CLI) of an affected device. This vulnerability stems from insufficient CSRF protections implemented in the web management interface, enabling attackers to trick authenticated administrators into executing malicious actions.

The attack requires user interaction—an authenticated administrator must be persuaded to click a crafted malicious link. Upon successful exploitation, the attacker can perform arbitrary actions on the affected network device with the privileges of the targeted user, potentially leading to complete device compromise and network infrastructure manipulation.

Critical Impact

An unauthenticated remote attacker can execute arbitrary CLI commands on Cisco IOS XE devices by exploiting insufficient CSRF protections, potentially gaining full control over critical network infrastructure.

Affected Products

• Cisco IOS XE versions 17.3.2 through 17.3.8a
• Cisco IOS XE versions 17.4.1 through 17.4.2a
• Cisco IOS XE versions 17.5.1 through 17.12.1y

Discovery Timeline

• September 25, 2024 - CVE-2024-20437 published to NVD
• October 24, 2024 - Last updated in NVD database

Technical Details for CVE-2024-20437

Vulnerability Analysis

This CSRF vulnerability (CWE-352) exists because the Cisco IOS XE web-based management interface fails to properly validate the authenticity of requests submitted by authenticated users. Web applications typically implement CSRF protections through anti-CSRF tokens, same-site cookie attributes, or origin header verification. In this case, the affected versions of Cisco IOS XE do not adequately implement these security controls.

The vulnerability is exploitable over the network without requiring prior authentication to the target device. However, successful exploitation depends on social engineering—the attacker must convince a logged-in administrator to visit a malicious webpage or click a crafted link while their management session is active. The scope of impact includes complete confidentiality, integrity, and availability compromise of the affected device.

Root Cause

The root cause of CVE-2024-20437 is insufficient CSRF protection mechanisms in the web-based management interface of Cisco IOS XE Software. The interface fails to properly validate that state-changing requests originate from legitimate user actions rather than cross-origin requests initiated by attacker-controlled content. This lack of proper request origin validation allows attackers to craft malicious requests that execute privileged CLI commands when an authenticated administrator's browser is tricked into submitting them.

Attack Vector

The attack vector involves an attacker hosting a malicious webpage containing hidden forms or JavaScript that automatically submits requests to the target Cisco IOS XE device's management interface. When an administrator who is already authenticated to the device visits this malicious page, their browser automatically includes valid session credentials with the forged request.

The attacker's crafted request can contain any CLI command that the targeted user has permission to execute. Since network administrators typically have elevated privileges, successful exploitation could allow attackers to modify device configurations, create backdoor accounts, disable security features, or disrupt network operations.

A typical CSRF attack scenario involves embedding a hidden form in a malicious webpage that targets the Cisco IOS XE management URL. When the authenticated victim visits the attacker's page, JavaScript automatically submits the form, executing commands such as creating new administrative users or modifying access control lists. The victim's browser includes valid session cookies, making the malicious request appear legitimate to the target device.

Detection Methods for CVE-2024-20437

Indicators of Compromise

• Unexpected configuration changes on Cisco IOS XE devices, particularly new user accounts or modified access lists
• Web server logs showing unusual request patterns to the management interface from unfamiliar referrer URLs
• Authentication logs indicating administrative actions occurring without corresponding legitimate administrator activity
• Unauthorized modifications to routing tables, ACLs, or other critical network configurations

Detection Strategies

• Review Cisco IOS XE device logs for configuration changes that administrators did not authorize
• Implement web application firewall rules to detect and block requests with suspicious referrer headers targeting device management interfaces
• Monitor for outbound connections from administrator workstations to known malicious domains or newly registered domains
• Enable detailed logging of all management interface access and correlate with administrator activity records

Monitoring Recommendations

• Configure SIEM alerts for any configuration changes on critical network infrastructure devices outside of scheduled maintenance windows
• Implement network monitoring to detect unexpected management interface access patterns
• Enable AAA accounting on all Cisco IOS XE devices to maintain comprehensive audit trails of administrative actions
• Regularly audit device configurations against baseline templates to identify unauthorized modifications

How to Mitigate CVE-2024-20437

Immediate Actions Required

• Apply the latest Cisco IOS XE software updates as detailed in the Cisco Security Advisory
• Restrict access to the web-based management interface to trusted management networks only
• Implement network segmentation to isolate management plane traffic from user traffic
• Educate administrators about CSRF attacks and the importance of not clicking links or visiting untrusted websites while logged into network management interfaces

Patch Information

Cisco has released software updates that address this vulnerability. Customers should consult the Cisco Security Advisory cisco-sa-webui-csrf-ycUYxkKO for specific version information and upgrade paths. Organizations running affected versions (17.3.x through 17.12.x) should prioritize patching based on the device's network criticality and exposure.

Workarounds

• Disable the HTTP/HTTPS web-based management interface if not required for operations, using CLI-only management instead
• Configure access control lists to limit management interface access to specific trusted IP addresses
• Use a dedicated out-of-band management network that is isolated from production traffic and internet access
• Implement browser session isolation for administrators, using separate browser profiles or virtual machines for network device management

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

# Alternatively, restrict HTTP server access to specific management VLAN
configure terminal
ip http access-class 10
access-list 10 permit 10.10.10.0 0.0.0.255
access-list 10 deny any
end
write memory