CVE-2021-33304
📋 TL;DR
A double free vulnerability in picoTCP's fragment reassembly function allows attackers to execute arbitrary code by triggering memory corruption. This affects systems using picoTCP v1.7.0 or picoTCP-NG v2.1 for network communication. Attackers can potentially gain full control of affected systems.
💻 Affected Systems
- picoTCP
- picoTCP-NG
📦 What is this software?
Picotcp by Altran
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, and persistent backdoor installation.
Likely Case
Denial of service through system crashes or instability, with potential for remote code execution in targeted attacks.
If Mitigated
Limited to denial of service if memory protections are enabled, but still potentially exploitable for code execution.
🎯 Exploit Status
The vulnerability is in network packet processing, making remote exploitation possible without authentication. Public GitHub issues demonstrate the bug.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: picoTCP-NG v2.1.1 or later
Vendor Advisory: https://github.com/virtualsquare/picotcp/issues/6
Restart Required: Yes
Instructions:
1. Update picoTCP-NG to version 2.1.1 or later. 2. Recompile any applications using the library. 3. Restart affected services or systems.
🔧 Temporary Workarounds
Disable IP fragment reassembly
linuxConfigure systems to drop fragmented IP packets to prevent triggering the vulnerable code path.
iptables -A INPUT -f -j DROP
iptables -A FORWARD -f -j DROP
Network filtering
allUse network firewalls or IPS to block fragmented packets destined for vulnerable systems.
🧯 If You Can't Patch
- Segment network to isolate vulnerable systems from untrusted networks
- Implement strict network monitoring for fragmented packet traffic patterns
🔍 How to Verify
Check if Vulnerable:
Check if picoTCP library version is 1.7.0 or picoTCP-NG version is 2.1. Review application dependencies and linked libraries.Check Version:
Check application documentation or build configuration for picoTCP version. For compiled applications, use: strings binary_name | grep -i picotcpVerify Fix Applied:
Verify picoTCP-NG version is 2.1.1 or later. Test fragment reassembly functionality after update.📡 Detection & Monitoring
Log Indicators:
- Application crashes or abnormal termination
- Memory allocation errors in system logs
- Unexpected process restarts
Network Indicators:
- Unusual fragmented IP traffic patterns
- Spike in malformed packet reception
SIEM Query:
source="application_logs" AND ("segmentation fault" OR "double free" OR "corrupted")