CVE-2022-20870 Overview
A vulnerability in the egress MPLS packet processing function of Cisco IOS XE Software for Cisco Catalyst 3650, Catalyst 3850, and Catalyst 9000 Family Switches could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to insufficient input validation of IPv4 traffic. An attacker could exploit this vulnerability by sending a malformed packet out of an affected MPLS-enabled interface. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.
Critical Impact
Remote attackers can cause network switches to unexpectedly reload by sending malformed MPLS packets, disrupting network availability without requiring authentication.
Affected Products
- Cisco IOS XE Software
- Cisco Catalyst 3650 Family Switches (all variants)
- Cisco Catalyst 3850 Family Switches (all variants)
- Cisco Catalyst 9300 Series Switches
- Cisco Catalyst 9400 Series Switches
- Cisco Catalyst 9500 Series Switches
- Cisco Catalyst 9600 Series Switches
Discovery Timeline
- 2022-10-10 - CVE-2022-20870 published to NVD
- 2024-11-21 - Last updated in NVD database
Technical Details for CVE-2022-20870
Vulnerability Analysis
This denial of service vulnerability exists in the egress MPLS (Multiprotocol Label Switching) packet processing function within Cisco IOS XE Software. The flaw specifically affects how the software handles IPv4 traffic that traverses MPLS-enabled interfaces on affected Catalyst switch platforms.
The vulnerability is exploitable remotely over the network without requiring any form of authentication or user interaction. When successfully exploited, the attack impacts systems beyond the vulnerable component itself, potentially affecting network availability for all connected devices and services. The primary impact is on system availability, as the attack forces a complete device reload.
Root Cause
The root cause of this vulnerability is insufficient input validation (CWE-130) when processing IPv4 traffic destined for egress through MPLS-enabled interfaces. The MPLS packet processing function fails to properly validate certain fields within malformed IPv4 packets before processing them, leading to a condition that triggers an unexpected device reload.
Attack Vector
An attacker can exploit this vulnerability by crafting and sending malformed IPv4 packets that are processed through an MPLS-enabled interface on the affected device. The attack requires:
- Network access to reach the vulnerable switch
- The target switch must have MPLS enabled on at least one interface
- The malformed packet must traverse the MPLS-enabled interface during egress processing
The attack does not require authentication, making it particularly dangerous in environments where network access control is not strictly enforced. Once the malformed packet reaches the egress MPLS processing function, insufficient validation causes the device to enter an unrecoverable state, forcing a reload.
Detection Methods for CVE-2022-20870
Indicators of Compromise
- Unexpected switch reloads or crashes in device logs
- System crash messages in syslog referencing MPLS packet processing
- Pattern of repeated device reboots correlating with high network traffic periods
- Crash dump files indicating exceptions in MPLS-related code paths
Detection Strategies
- Monitor for unexpected device reloads on affected Catalyst switches using SNMP traps or syslog alerts
- Implement network anomaly detection to identify unusual patterns of malformed IPv4 packets
- Review crash information using show logging and show version commands to identify MPLS-related crashes
- Configure automated alerting for switch availability using network monitoring tools
Monitoring Recommendations
- Enable comprehensive logging on all MPLS-enabled interfaces
- Configure SNMP notifications for device reload events and interface state changes
- Implement baseline traffic analysis to detect anomalous packet patterns targeting MPLS infrastructure
- Set up redundant monitoring paths to detect switch unavailability during reload events
How to Mitigate CVE-2022-20870
Immediate Actions Required
- Review the Cisco Security Advisory for fixed software versions
- Identify all affected Catalyst switches in your environment running Cisco IOS XE with MPLS enabled
- Plan and schedule firmware updates to patched versions during maintenance windows
- Implement network segmentation to limit exposure of MPLS-enabled interfaces
Patch Information
Cisco has released security updates to address this vulnerability. Administrators should consult the Cisco Security Advisory cisco-sa-iosxe-mpls-dos-Ab4OUL3 for specific fixed software versions applicable to their hardware platforms. The advisory provides detailed information on affected and fixed releases for each Catalyst switch family.
Workarounds
- Where operationally feasible, disable MPLS on interfaces that do not require it to reduce the attack surface
- Implement access control lists (ACLs) to filter potentially malicious traffic before it reaches MPLS-enabled interfaces
- Consider network segmentation to limit which network segments can send traffic to MPLS-enabled switches
- Ensure redundant network paths exist to maintain connectivity during potential device reloads
# Verify MPLS configuration on interfaces
show mpls interfaces
# Check current IOS XE version
show version
# Review device crash history
show logging | include reload|crash
# Verify applied access lists
show ip access-lists
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
