CVE-2023-20067: Cisco IOS XE DoS Vulnerability

CVE-2023-20067 Overview

A vulnerability in the HTTP-based client profiling feature of Cisco IOS XE Software for Wireless LAN Controllers (WLCs) could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient input validation of received traffic. An attacker could exploit this vulnerability by sending crafted traffic through a wireless access point. A successful exploit could allow the attacker to cause CPU utilization to increase, which could result in a DoS condition on an affected device and could cause new wireless client associations to fail.

Critical Impact

Successful exploitation causes CPU exhaustion leading to denial of service, preventing new wireless client associations until the attack traffic stops.

Affected Products

• Cisco IOS XE versions 16.10.x through 16.12.x
• Cisco IOS XE versions 17.1.x through 17.9.1
• Cisco Wireless LAN Controllers running affected IOS XE versions

Discovery Timeline

• March 23, 2023 - CVE-2023-20067 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-20067

Vulnerability Analysis

This vulnerability exists within the HTTP-based client profiling feature of Cisco IOS XE Software specifically when deployed on Wireless LAN Controllers. The flaw stems from insufficient input validation of received traffic, allowing an attacker within the adjacent network to send specially crafted traffic through a wireless access point that causes excessive CPU utilization on the target device.

The vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling), indicating that the affected component fails to properly limit resource consumption when processing certain types of traffic. This design flaw allows an attacker to force the system into a resource exhaustion state without requiring any authentication or privileges.

The attack requires the attacker to be on the same network segment as the target (adjacent network access), but once positioned, exploitation is straightforward with low attack complexity. The impact is limited to availability—no confidentiality or integrity impact occurs—but the DoS condition can significantly disrupt wireless network operations.

Root Cause

The root cause of CVE-2023-20067 is insufficient input validation in the HTTP-based client profiling feature. When processing traffic from wireless clients, the WLC fails to properly validate and limit the resources allocated to handle certain crafted packets. This allows malformed or excessive traffic to consume CPU resources without appropriate throttling or bounds checking, leading to resource exhaustion (CWE-770).

Attack Vector

The attack vector is adjacent network access, meaning an attacker must be within the same network segment or Layer 2 broadcast domain as the target device. The attacker sends crafted traffic through a wireless access point managed by the vulnerable WLC. The malicious traffic is processed by the HTTP-based client profiling feature, which due to the insufficient input validation, causes the CPU to spike. The attack does not require any authentication or user interaction. Once the offending traffic is stopped, the system returns to an operational state and new client associations succeed.

Detection Methods for CVE-2023-20067

Indicators of Compromise

• Sudden and sustained increase in CPU utilization on Wireless LAN Controllers running Cisco IOS XE
• Failed wireless client association attempts that coincide with high CPU usage
• Unusual or malformed HTTP traffic patterns originating from wireless clients
• Degraded performance or unresponsiveness of WLC management interfaces during suspected attack periods

Detection Strategies

• Monitor CPU utilization thresholds on all Cisco WLC devices and alert on sustained spikes above baseline
• Implement network traffic analysis to identify anomalous traffic patterns directed at wireless access points
• Deploy SentinelOne Singularity to detect and correlate suspicious network behavior across the wireless infrastructure
• Enable logging for the HTTP-based client profiling feature and review for unusual activity

Monitoring Recommendations

• Establish baseline CPU metrics for all Cisco IOS XE WLCs and configure SNMP traps for threshold violations
• Implement centralized log collection from WLC devices to enable correlation of CPU events with network traffic
• Use SentinelOne's network visibility capabilities to monitor adjacent network segments for attack indicators
• Regularly review wireless client association logs for patterns indicating DoS attempts

How to Mitigate CVE-2023-20067

Immediate Actions Required

• Review the Cisco Security Advisory to determine if your deployed version is affected
• Prioritize patching of internet-facing and critical wireless infrastructure running vulnerable IOS XE versions
• Implement network segmentation to limit adjacent network access to WLCs where feasible
• Enable enhanced monitoring on affected devices until patches can be applied

Patch Information

Cisco has released software updates that address this vulnerability. Administrators should consult the Cisco Security Advisory for specific fixed software versions and upgrade guidance. The advisory provides detailed information on which IOS XE versions contain the fix and recommended upgrade paths based on your current deployment.

Workarounds

• Consider disabling the HTTP-based client profiling feature if it is not required for your environment (consult Cisco documentation for operational impact)
• Implement strict network access controls to limit which devices can communicate with WLC infrastructure
• Deploy additional network monitoring to detect and alert on potential exploitation attempts
• Segment wireless management networks from general user traffic where architecturally feasible

# Example: Check current IOS XE version on WLC
show version | include IOS XE

# Example: Monitor CPU utilization for anomalies
show processes cpu sorted | head 20

# Example: Review wireless client associations
show wireless client summary