CVE-2021-41121
📋 TL;DR
CVE-2021-41121 is a memory corruption vulnerability in Vyper smart contract language that occurs when performing function calls inside literal structs. This allows attackers to potentially execute arbitrary code or cause denial of service on affected smart contracts. Anyone using Vyper versions before 0.3.0 for Ethereum smart contract development is affected.
💻 Affected Systems
- Vyper
📦 What is this software?
Vyper by Vyperlang
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of smart contract functionality leading to fund theft, contract destruction, or arbitrary code execution on the EVM
Likely Case
Smart contract crashes or unexpected behavior leading to denial of service and potential financial losses
If Mitigated
No impact if contracts are deployed with patched Vyper compiler
🎯 Exploit Status
Exploitation requires crafting specific smart contract code that triggers the memory corruption. No public exploits have been documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.3.0
Vendor Advisory: https://github.com/vyperlang/vyper/security/advisories/GHSA-xv8x-pr4h-73jv
Restart Required: No
Instructions:
1. Update Vyper using pip: 'pip install vyper==0.3.0' 2. Recompile all smart contracts with the updated compiler 3. Redeploy any contracts compiled with vulnerable versions
🔧 Temporary Workarounds
Avoid literal struct function calls
allManually review and modify smart contract code to avoid function calls inside literal structs
🧯 If You Can't Patch
- Audit all smart contracts for function calls inside literal structs and remove vulnerable patterns
- Implement additional security controls and monitoring for contracts that cannot be recompiled
🔍 How to Verify
Check if Vulnerable:
Check Vyper version with 'vyper --version'. If version is below 0.3.0, you are vulnerableCheck Version:
vyper --versionVerify Fix Applied:
Verify installation with 'vyper --version' shows 0.3.0 or higher📡 Detection & Monitoring
Log Indicators:
- Smart contract compilation errors
- Unexpected contract behavior or crashes
Network Indicators:
- Unusual transaction patterns targeting vulnerable contracts
- Failed contract executions
SIEM Query:
Not applicable - blockchain transactions are not typically monitored by traditional SIEM systems