CVE-2021-26777
📋 TL;DR
This CVE describes a critical buffer overflow vulnerability in the SetFirewall function of CIRCUTOR COMPACT DC-S BASIC smart metering concentrators. Attackers can exploit this to execute arbitrary code with potentially full system control. Organizations using these specific concentrators with vulnerable firmware are affected.
💻 Affected Systems
- CIRCUTOR COMPACT DC-S BASIC smart metering concentrator
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the concentrator allowing attackers to execute arbitrary code, potentially gaining persistent access, disrupting metering operations, or pivoting to other industrial control systems.
Likely Case
Remote code execution leading to concentrator compromise, data manipulation, service disruption, or use as a foothold in industrial networks.
If Mitigated
Limited impact if network segmentation isolates concentrators and strict access controls prevent exploitation attempts.
🎯 Exploit Status
Public GitHub repository contains vulnerability details and likely exploitation methods. Buffer overflow vulnerabilities in embedded devices are frequently weaponized.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Unknown
Restart Required: Yes
Instructions:
1. Contact CIRCUTOR for firmware updates or patches. 2. If update available, download from vendor portal. 3. Apply firmware update following vendor instructions. 4. Verify successful update and functionality.
🔧 Temporary Workarounds
Network Segmentation
allIsolate concentrators in dedicated network segments with strict firewall rules
Access Control
allRestrict network access to concentrator management interfaces to authorized IPs only
🧯 If You Can't Patch
- Implement strict network segmentation to isolate concentrators from untrusted networks
- Deploy intrusion detection/prevention systems to monitor for exploitation attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface or console. If version is CIR_CDC_v1.2.17, device is vulnerable.Check Version:
Check via web interface or consult device documentation for version checking commandsVerify Fix Applied:
Verify firmware version has been updated to a version later than CIR_CDC_v1.2.17📡 Detection & Monitoring
Log Indicators:
- Unusual access to index.cgi with SetFirewall parameters
- Buffer overflow error messages in system logs
- Unexpected process execution
Network Indicators:
- Unusual HTTP requests to concentrator web interface with crafted SetFirewall parameters
- Traffic patterns indicating exploitation attempts
SIEM Query:
source="concentrator_logs" AND (uri="*/index.cgi*" AND params="*SetFirewall*")