CVE-2023-20033 Overview
A denial of service vulnerability exists in Cisco IOS XE Software affecting Cisco Catalyst 3650 and Catalyst 3850 Series Switches. This vulnerability allows an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. The flaw stems from improper resource management when processing traffic received on the management interface, enabling attackers to disrupt network operations by sending high volumes of traffic to the management interface.
Critical Impact
Unauthenticated remote attackers can cause network switches to reload, disrupting enterprise network connectivity and potentially affecting all connected devices and services.
Affected Products
- Cisco IOS XE Software versions 16.3.1 through 16.12.9
- Cisco Catalyst 3650 Series Switches (all variants including 12x48, 24, and 48-port models)
- Cisco Catalyst 3850 Series Switches (all variants including 12, 24, 32, and 48-port models)
Discovery Timeline
- September 27, 2023 - CVE-2023-20033 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2023-20033
Vulnerability Analysis
This vulnerability (classified under CWE-770: Allocation of Resources Without Limits or Throttling) affects the management interface processing capabilities of Cisco Catalyst 3650 and 3850 Series Switches running vulnerable versions of IOS XE Software. The core issue lies in how the switch handles incoming traffic on its management interface without proper resource constraints or rate limiting mechanisms.
When the management interface receives network traffic, the affected software fails to properly manage system resources during packet processing. This lack of resource management creates a condition where an attacker can overwhelm the device's processing capabilities by flooding the management interface with traffic at a high rate.
The vulnerability can be exploited remotely without authentication, meaning any attacker with network access to the management interface can trigger the condition. This is particularly concerning in enterprise environments where these switches often serve as critical infrastructure components.
Root Cause
The root cause of this vulnerability is improper resource management within the Cisco IOS XE Software when processing traffic on the management interface. Specifically, the software does not implement adequate controls to limit resource allocation or throttle incoming traffic rates, allowing system resources to become exhausted under high traffic conditions. This resource exhaustion triggers a defensive reload of the device, causing the denial of service condition.
Attack Vector
The attack vector for CVE-2023-20033 is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:
- Identifying a vulnerable Cisco Catalyst 3650 or 3850 Series Switch with an accessible management interface
- Sending a high rate of network traffic directed at the management interface
- The excessive traffic causes improper resource allocation within the switch
- Resource exhaustion triggers an unexpected device reload
- The reload causes a denial of service for all network traffic passing through the switch
The attack does not require sophisticated techniques or specialized tools—standard traffic generation utilities can be used to flood the management interface with packets at rates sufficient to trigger the vulnerability.
Detection Methods for CVE-2023-20033
Indicators of Compromise
- Unexpected switch reloads or crashes in Catalyst 3650/3850 Series Switches without apparent cause
- High volumes of traffic directed at the switch management interface IP address
- System logs showing resource exhaustion or memory allocation failures prior to reload
- Repeated crashinfo or crash dump files on affected devices
Detection Strategies
- Monitor management interface traffic patterns for anomalous high-rate traffic flows
- Configure syslog alerting for unexpected device reload events on Catalyst 3650/3850 switches
- Implement network flow analysis to detect traffic flooding patterns targeting management interfaces
- Review IOS XE system logs for resource allocation warnings or errors
Monitoring Recommendations
- Deploy network monitoring solutions to track traffic volume to switch management interfaces
- Configure SNMP traps for device reload events and CPU/memory utilization spikes
- Implement baseline monitoring for management interface traffic to identify deviations
- Use SentinelOne Singularity platform for network asset visibility and anomaly detection
How to Mitigate CVE-2023-20033
Immediate Actions Required
- Review and identify all Cisco Catalyst 3650 and 3850 Series Switches in your environment running vulnerable IOS XE versions
- Apply access control lists (ACLs) to restrict management interface access to trusted administrative networks only
- Upgrade affected devices to a patched version of Cisco IOS XE Software as recommended in the Cisco Security Advisory
- Implement out-of-band management networks to isolate management traffic from production network traffic
Patch Information
Cisco has released software updates that address this vulnerability. Organizations should consult the Cisco Security Advisory for specific fixed software versions and upgrade guidance. The advisory provides detailed information about affected releases and the recommended upgrade paths for Cisco IOS XE Software on Catalyst 3650 and 3850 Series Switches.
Workarounds
- Implement infrastructure ACLs (iACLs) to filter traffic to the management interface from untrusted sources
- Configure control plane policing (CoPP) to rate-limit traffic destined to the management interface
- Isolate the management interface on a dedicated management VLAN with restricted access
- Deploy network-based rate limiting on upstream devices to prevent traffic flooding to switch management interfaces
# Example ACL configuration to restrict management interface access
! Configure ACL to permit only trusted management networks
ip access-list extended MGMT-ACCESS
permit ip 10.10.10.0 0.0.0.255 any
permit ip 192.168.1.0 0.0.0.255 any
deny ip any any log
! Apply ACL to management interface
interface GigabitEthernet0/0
ip access-group MGMT-ACCESS in
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
