CVE-2020-27541
📋 TL;DR
CVE-2020-27541 is a denial-of-service vulnerability in Rostelecom CS-C2SHW IP camera firmware. It allows remote attackers to crash the AgentGreen service by sending a specially crafted small UDP broadcast packet, causing the service to restart. This affects users of Rostelecom CS-C2SHW IP cameras with vulnerable firmware.
💻 Affected Systems
- Rostelecom CS-C2SHW IP Camera
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Persistent service disruption causing camera unavailability, potentially affecting security monitoring capabilities.
Likely Case
Intermittent camera service restarts leading to temporary loss of video feed and functionality.
If Mitigated
Minimal impact with proper network segmentation and monitoring in place.
🎯 Exploit Status
Exploitation requires sending a malformed UDP packet to port 37020. The vulnerability is well-documented in public research.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
No official patch available. Consider upgrading to newer firmware versions if available from vendor.
🔧 Temporary Workarounds
Network Segmentation
allIsolate cameras on separate VLANs and restrict UDP traffic to port 37020
Firewall Rules
linuxBlock UDP port 37020 from untrusted networks
iptables -A INPUT -p udp --dport 37020 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate cameras from untrusted networks
- Monitor for UDP traffic to port 37020 and implement rate limiting
🔍 How to Verify
Check if Vulnerable:
Check firmware version via camera web interface or SSH if available. Version 5.0.082.1 is vulnerable.Check Version:
Check camera web interface at System > Version or via SSH if enabledVerify Fix Applied:
Verify firmware has been updated to a version newer than 5.0.082.1📡 Detection & Monitoring
Log Indicators:
- AgentGreen service restart logs
- Unexpected process termination
Network Indicators:
- UDP packets to port 37020 with small payload size
- Multiple connection attempts to camera UDP port
SIEM Query:
source_port=37020 AND protocol=UDP AND packet_size<50