CVE-2021-21257
📋 TL;DR
This vulnerability allows attackers to perform out-of-bounds memory writes by injecting specially crafted packets into Contiki-NG's RPL routing implementation. It affects IoT devices running Contiki-NG versions before 4.6, potentially leading to remote code execution or system crashes. The issue stems from insufficient validation of source routing header fields.
💻 Affected Systems
- Contiki-NG operating system
📦 What is this software?
Contiki Ng by Contiki Ng
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistence, and lateral movement within IoT networks.
Likely Case
Denial of service through system crashes or memory corruption, potentially disrupting IoT network operations.
If Mitigated
No impact if patched or if network segmentation prevents malicious packet injection.
🎯 Exploit Status
Exploitation requires network access to inject packets but no authentication. The vulnerability is in core routing code that processes network packets.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Contiki-NG 4.6
Vendor Advisory: https://github.com/contiki-ng/contiki-ng/security/advisories/GHSA-mvc7-9p4q-c5cm
Restart Required: Yes
Instructions:
1. Update Contiki-NG to version 4.6 or later. 2. Rebuild and redeploy firmware to affected IoT devices. 3. Restart devices to apply the updated firmware.
🔧 Temporary Workarounds
Apply GitHub patch manually
allApply the specific fix from GitHub pull request #1431 to validate CMPR field before using addr_ptr.
git apply https://github.com/contiki-ng/contiki-ng/pull/1431.patch
🧯 If You Can't Patch
- Segment IoT networks to prevent unauthorized packet injection
- Implement network monitoring for anomalous RPL traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check Contiki-NG version in device firmware or source code. If version < 4.6 and using RPL routing, device is vulnerable.Check Version:
Check CONTIKI_VERSION_STRING in contiki-version.h or device firmware versionVerify Fix Applied:
Verify Contiki-NG version is 4.6 or later and confirm the memcpy calls in rpl-ext-header.c have proper bounds checking.📡 Detection & Monitoring
Log Indicators:
- System crashes, memory corruption errors, unexpected device reboots
Network Indicators:
- Malformed RPL source routing headers, unusual packet injection patterns
SIEM Query:
Search for: (device_type:iot OR os:contiki) AND (event_type:crash OR error:memory_corruption)