CVE-2022-20846: Cisco IOS XR Buffer Overflow Vulnerability

CVE-2022-20846 Overview

A heap buffer overflow vulnerability exists in the Cisco Discovery Protocol (CDP) implementation for Cisco IOS XR Software. This vulnerability could allow an unauthenticated, adjacent attacker to cause the CDP process to reload on affected devices by sending specially crafted CDP packets.

The vulnerability arises from improper handling of certain CDP messages, leading to a heap buffer overflow condition. While the bytes that can be written in the overflow are restricted—limiting remote code execution potential—a successful exploit still enables denial of service through process crashes.

Critical Impact

An unauthenticated attacker on the same Layer 2 broadcast domain can cause CDP process reloads on vulnerable Cisco IOS XR devices, potentially disrupting network discovery and management operations.

Affected Products

• Cisco IOS XR versions 6.5.x (6.5.1 through 6.5.93)
• Cisco IOS XR versions 6.6.x through 6.9.x
• Cisco IOS XR versions 7.0.x through 7.6.x

Discovery Timeline

• November 15, 2024 - CVE-2022-20846 published to NVD
• August 05, 2025 - Last updated in NVD database

Technical Details for CVE-2022-20846

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The flaw exists in how Cisco IOS XR Software processes incoming CDP packets, where insufficient bounds checking on packet data allows an attacker to overflow a heap-allocated buffer.

CDP operates at Layer 2 of the OSI model, meaning exploitation requires the attacker to be in the same broadcast domain as the targeted device. This adjacency requirement limits the attack surface to local network segments, but within enterprise environments, this could still represent significant exposure across data center or campus networks where CDP is commonly enabled for device discovery and management.

The restricted nature of the bytes that can be written during the overflow limits the ability to achieve arbitrary code execution, but the denial of service impact through process crashes remains a viable attack outcome.

Root Cause

The root cause is a heap buffer overflow vulnerability in the CDP message parsing code within Cisco IOS XR Software. When processing malformed or oversized CDP packets, the software fails to properly validate the size of input data before copying it into a fixed-size heap buffer, resulting in a buffer overflow condition.

Attack Vector

The attack requires adjacent network access, meaning the attacker must be positioned within the same Layer 2 broadcast domain as the target device. No authentication or user interaction is required for exploitation. The attacker sends a maliciously crafted CDP packet to the affected device, which triggers the heap buffer overflow when the CDP process attempts to parse the packet.

Since CDP is a link-layer protocol, the malicious packet is processed by any CDP-enabled interface receiving it. Network segmentation and VLAN isolation can help limit exposure, but any device sharing a Layer 2 segment with the attacker is potentially vulnerable.

The vulnerability mechanism involves malformed CDP packets that exceed expected buffer boundaries during message parsing. When the CDP process receives these specially crafted packets, it attempts to copy data into a heap buffer without adequate size validation, leading to memory corruption and subsequent process termination. Technical details are available in the Cisco Security Advisory.

Detection Methods for CVE-2022-20846

Indicators of Compromise

• Unexpected CDP process crashes or restarts on Cisco IOS XR devices
• System logs showing CDP process termination with memory-related errors
• Unusual CDP packet activity or malformed CDP frames captured in network traffic
• Repeated CDP service interruptions correlating with suspicious network activity

Detection Strategies

• Monitor system logs for CDP process crashes using syslog collection and SIEM correlation
• Implement network packet capture on critical segments to detect malformed CDP packets
• Deploy IDS/IPS rules to identify anomalous CDP traffic patterns
• Review device health monitoring for unexpected CDP service restarts

Monitoring Recommendations

• Enable logging of CDP-related events on affected Cisco IOS XR devices
• Configure SNMP traps for process failures to receive real-time alerts
• Establish baseline CDP traffic patterns to identify anomalies
• Implement centralized log aggregation for cross-device correlation

How to Mitigate CVE-2022-20846

Immediate Actions Required

• Identify all Cisco IOS XR devices running vulnerable versions (6.5.x through 7.6.x)
• Apply Cisco security updates as described in the vendor advisory
• Consider disabling CDP on interfaces where it is not required
• Implement network segmentation to limit Layer 2 adjacency exposure

Patch Information

Cisco has released software updates that address this vulnerability. Organizations should consult the Cisco Security Advisory for CVE-2022-20846 for specific fixed software versions and upgrade guidance. This advisory was part of the September 2022 release of the Cisco IOS XR Software Security Advisory Bundled Publication.

Workarounds

• There are no workarounds that address this vulnerability according to Cisco
• As a defense-in-depth measure, disable CDP on interfaces not requiring device discovery
• Implement strict Layer 2 network segmentation to limit attacker adjacency
• Consider using Link Layer Discovery Protocol (LLDP) as an alternative where CDP is not essential

# Disable CDP on specific interfaces (defense-in-depth measure only)
interface GigabitEthernet0/0/0/0
  no cdp

# Disable CDP globally if not required
no cdp