CVE-2021-22393
📋 TL;DR
A denial-of-service vulnerability exists in Huawei CloudEngine switches where attackers can send specific messages to exhaust system resources. This affects CloudEngine 5800, 6800, 7800, and 12800 series switches running vulnerable software versions. Successful exploitation disrupts normal network services.
💻 Affected Systems
- CloudEngine 5800
- CloudEngine 6800
- CloudEngine 7800
- CloudEngine 12800
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption of affected switches, causing network outages for connected systems and services.
Likely Case
Degraded switch performance leading to packet loss, latency, and intermittent connectivity issues.
If Mitigated
Minimal impact with proper network segmentation and traffic filtering in place.
🎯 Exploit Status
Exploitation requires sending a large amount of specific messages to trigger the DoS condition. No authentication is required to send these messages.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Huawei security advisory for specific patched versions
Vendor Advisory: https://www.huawei.com/en/psirt/security-advisories/huawei-sa-20210324-01-dos-en
Restart Required: Yes
Instructions:
1. Review Huawei security advisory SA-20210324-01. 2. Identify affected switch models and versions. 3. Download appropriate firmware updates from Huawei support portal. 4. Apply updates following Huawei's upgrade procedures. 5. Reboot switches to activate patched firmware.
🔧 Temporary Workarounds
Network Access Control
allRestrict access to switch management interfaces using ACLs to prevent unauthorized message traffic
# Example ACL to restrict management access
# acl number 3000
# rule 5 permit ip source 10.0.0.0 0.255.255.255
# rule 10 deny ip
Traffic Rate Limiting
allImplement rate limiting on switch interfaces to prevent flood attacks
# Example traffic policing configuration
# traffic classifier attack
# if-match any
# traffic behavior attack
# car cir 1000
# traffic policy attack
# classifier attack behavior attack
# interface GigabitEthernet0/0/1
# traffic-policy attack inbound
🧯 If You Can't Patch
- Isolate affected switches in separate VLANs with strict access controls
- Implement network monitoring to detect and alert on unusual message patterns
🔍 How to Verify
Check if Vulnerable:
Check switch version using 'display version' command and compare against Huawei's affected version list in advisory SA-20210324-01Check Version:
display versionVerify Fix Applied:
After patching, verify firmware version with 'display version' command matches patched versions listed in Huawei advisory📡 Detection & Monitoring
Log Indicators:
- Unusual increase in error messages
- System resource exhaustion alerts
- Interface flapping or instability logs
Network Indicators:
- Sudden increase in specific message types to switch management interfaces
- Unusual traffic patterns to switch control plane
SIEM Query:
source="switch_logs" AND (message="resource exhaustion" OR message="system busy" OR message="packet drop")