CVE-2020-14934
📋 TL;DR
CVE-2020-14934 is a critical buffer overflow vulnerability in Contiki-NG's SNMP agent that allows remote attackers to write arbitrary data beyond allocated buffer boundaries. This can lead to memory corruption and potential remote code execution on affected IoT devices running Contiki-NG 4.4 through 4.5. The vulnerability affects any device using the vulnerable SNMP implementation without proper input validation.
💻 Affected Systems
- Contiki-NG
📦 What is this software?
Contiki Ng by Contiki Ng
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, data exfiltration, or device becoming part of a botnet.
Likely Case
Device crash/DoS through memory corruption, with potential for arbitrary code execution by skilled attackers.
If Mitigated
Limited impact if SNMP is disabled or network access is restricted, though memory corruption could still occur from internal threats.
🎯 Exploit Status
Proof-of-concept details are available in public references. The vulnerability requires crafting malicious SNMP packets but doesn't require authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Contiki-NG 4.6 and later
Vendor Advisory: https://github.com/contiki-ng/contiki-ng/issues/1352
Restart Required: Yes
Instructions:
1. Update Contiki-NG to version 4.6 or later. 2. Recompile and redeploy firmware to affected devices. 3. Restart devices to apply the updated firmware.
🔧 Temporary Workarounds
Disable SNMP Agent
allDisable the SNMP agent if not required for device functionality.
# In Contiki-NG configuration, set: # #define UIP_CONF_SNMP 0
# Recompile and redeploy firmware
Network Segmentation
linuxRestrict SNMP traffic to trusted management networks only.
# Firewall rules example (Linux):
iptables -A INPUT -p udp --dport 161 -s TRUSTED_NETWORK -j ACCEPT
iptables -A INPUT -p udp --dport 161 -j DROP
🧯 If You Can't Patch
- Implement strict network access controls to block all SNMP traffic (UDP port 161) to affected devices from untrusted sources.
- Monitor devices for abnormal behavior or crashes that might indicate exploitation attempts.
🔍 How to Verify
Check if Vulnerable:
Check Contiki-NG version: if between 4.4 and 4.5 inclusive and SNMP is enabled, the device is vulnerable.Check Version:
# In Contiki-NG source/build directory: grep CONTIKI_VERSION_STRING project-conf.h or similar version fileVerify Fix Applied:
Verify Contiki-NG version is 4.6 or later and test SNMP functionality with valid and malformed requests.📡 Detection & Monitoring
Log Indicators:
- Device crashes/reboots
- Memory corruption errors in system logs
- Abnormal SNMP traffic patterns
Network Indicators:
- Malformed SNMP packets with excessive variable bindings
- SNMP traffic from unexpected sources
SIEM Query:
source_port=161 AND (packet_size>threshold OR pattern_match='malformed_snmp')