CVE-2022-20846
📋 TL;DR
A heap buffer overflow vulnerability in Cisco Discovery Protocol (CDP) implementation for Cisco IOS XR Software allows unauthenticated adjacent attackers to cause the CDP process to reload. This affects devices running vulnerable IOS XR versions where CDP is enabled. Attackers must be Layer 2 adjacent to exploit this vulnerability.
💻 Affected Systems
- Cisco IOS XR Software
📦 What is this software?
Ios Xr by Cisco
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⚠️ Risk & Real-World Impact
Worst Case
Denial of service through CDP process reload, potentially disrupting network discovery and management functions. Remote code execution is limited due to restricted bytes in the overflow.
Likely Case
Service disruption of CDP functionality, causing temporary loss of neighbor discovery information until process restarts.
If Mitigated
Minimal impact if CDP is disabled or devices are patched, as the vulnerability requires Layer 2 adjacency and CDP to be enabled.
🎯 Exploit Status
Exploitation requires sending specially crafted CDP packets, but attacker must be Layer 2 adjacent. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Refer to Cisco advisories for specific fixed versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xr-cdp-wnALzvT2
Restart Required: Yes
Instructions:
1. Check current IOS XR version. 2. Review Cisco advisories for fixed versions. 3. Download and install appropriate fixed software version. 4. Reboot device to apply changes.
🔧 Temporary Workarounds
Disable CDP
allCompletely disable Cisco Discovery Protocol on affected devices
no cdp enable
no cdp run
🧯 If You Can't Patch
- Disable CDP on all affected devices using 'no cdp enable' and 'no cdp run' commands
- Implement network segmentation to limit Layer 2 adjacency to trusted devices only
🔍 How to Verify
Check if Vulnerable:
Check IOS XR version with 'show version' and compare against vulnerable versions in Cisco advisoriesCheck Version:
show version | include Cisco IOS XRVerify Fix Applied:
Verify installed version matches fixed versions listed in Cisco advisories and confirm CDP is either disabled or device is patched📡 Detection & Monitoring
Log Indicators:
- CDP process crashes or reloads
- Unexpected CDP neighbor changes
- System logs showing CDP errors
Network Indicators:
- Malformed CDP packets on network
- Unusual CDP traffic patterns from untrusted sources
SIEM Query:
Search for 'CDP reload' or 'CDP crash' in system logs, monitor for CDP process restarts🔗 References
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-bng-Gmg5Gxt
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ncs4k-tl1-GNnLwC6
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-xr-cdp-wnALzvT2
