CVE-2020-29203
📋 TL;DR
CVE-2020-29203 is a critical buffer overflow vulnerability in struct2json library versions before 2020-11-18. Attackers can exploit this vulnerability to execute arbitrary code or cause denial of service by providing specially crafted input to the S2J_STRUCT_GET_string_ELEMENT function. Any application using vulnerable versions of struct2json for JSON parsing is affected.
💻 Affected Systems
- struct2json library
📦 What is this software?
Struct2json by Struct2json Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Application crash causing denial of service, potentially leading to data corruption or service disruption.
If Mitigated
Limited impact with proper input validation and memory protection mechanisms in place.
🎯 Exploit Status
Proof of concept available in GitHub issue. Exploitation is straightforward due to unsafe strcpy usage.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2020-11-18 or later
Vendor Advisory: https://github.com/armink/struct2json/issues/13
Restart Required: Yes
Instructions:
1. Update struct2json to version from 2020-11-18 or later. 2. Recompile all applications using the library. 3. Restart affected services.
🔧 Temporary Workarounds
Input Validation
allImplement strict input validation for all JSON parsing operations
Memory Protection
linuxEnable ASLR and DEP/Stack Canaries if available
gcc -fstack-protector-all -D_FORTIFY_SOURCE=2
🧯 If You Can't Patch
- Isolate vulnerable systems behind firewalls with strict network segmentation
- Implement WAF rules to block suspicious JSON payloads and buffer overflow attempts
🔍 How to Verify
Check if Vulnerable:
Check if application uses struct2json and examine version in source code or build artifactsCheck Version:
grep -r "struct2json" in source code or check library version in build configurationVerify Fix Applied:
Verify struct2json version is 2020-11-18 or later and strcpy has been replaced with safe alternatives📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults
- Unusual memory access patterns in application logs
Network Indicators:
- Large or malformed JSON payloads to services using struct2json
- Repeated connection attempts with varying payload sizes
SIEM Query:
source="application.logs" AND ("segmentation fault" OR "buffer overflow" OR "S2J_STRUCT_GET_string_ELEMENT")