CVE-2020-25111
📋 TL;DR
CVE-2020-25111 is a critical vulnerability in Contiki's IPv6 stack where insufficient validation of IPv6 header length allows attackers to cause denial-of-service or potentially execute arbitrary code via crafted ICMPv6 packets. This affects all systems running Contiki OS through version 3.0, particularly IoT devices and embedded systems using this operating system.
💻 Affected Systems
- Contiki OS
📦 What is this software?
Contiki Os by Contiki Os
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, allowing attackers to take control of affected devices.
Likely Case
Denial-of-service causing system crashes or instability, disrupting device functionality.
If Mitigated
Limited impact with proper network segmentation and filtering, though vulnerable systems remain at risk.
🎯 Exploit Status
Exploitation requires sending crafted ICMPv6 packets to vulnerable systems. The vulnerability is in the network stack, making it accessible to any network-adjacent attacker.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Contiki 3.x (post-3.0) or apply patches from Contiki-NG repository
Vendor Advisory: https://github.com/contiki-ng/contiki-ng/security/advisories
Restart Required: Yes
Instructions:
1. Update to latest Contiki-NG version. 2. Apply security patches for IPv6 header validation. 3. Recompile and redeploy firmware to affected devices. 4. Verify IPv6 stack handles malformed headers correctly.
🔧 Temporary Workarounds
Disable IPv6
allCompletely disable IPv6 functionality if not required
# Modify Contiki configuration to disable IPv6
# Set UIP_CONF_IPV6=0 in project-conf.h or contiki-conf.h
Network Filtering
linuxBlock ICMPv6 packets at network perimeter
# Example iptables rule for Linux gateways
iptables -A INPUT -p ipv6-icmp -j DROP
# Or block specific ICMPv6 types if possible
🧯 If You Can't Patch
- Segment vulnerable devices on isolated networks with strict firewall rules
- Implement network intrusion detection to monitor for ICMPv6 anomalies
🔍 How to Verify
Check if Vulnerable:
Check Contiki version and verify if IPv6 is enabled. Test with crafted ICMPv6 packets containing malformed headers.Check Version:
Check Contiki version in source code or firmware: grep CONTIKI_VERSION contiki-conf.h or similar configuration filesVerify Fix Applied:
Verify Contiki version is post-3.0 or patched. Test that malformed ICMPv6 packets are properly rejected without causing crashes.📡 Detection & Monitoring
Log Indicators:
- System crashes or reboots
- Kernel panic messages related to network stack
- Unusual ICMPv6 traffic logs
Network Indicators:
- Malformed ICMPv6 packets with abnormal header lengths
- Flood of ICMPv6 echo requests to Contiki devices
SIEM Query:
source="network" AND (proto="icmp6" OR icmp_type=128) AND (payload_length<40 OR header_length abnormal)