CVE-2022-29255
📋 TL;DR
CVE-2022-29255 is a vulnerability in Vyper smart contract language where external contract calls without return values could cause the contract address to be evaluated twice, potentially leading to incorrect execution outcomes. This affects developers using Vyper versions before 0.3.4 to write Ethereum smart contracts. The double evaluation could enable unexpected side effects and contract logic manipulation.
💻 Affected Systems
- Vyper
📦 What is this software?
Vyper by Vyperlang
⚠️ Risk & Real-World Impact
Worst Case
Smart contracts could execute unintended logic, leading to financial losses, token theft, or contract state corruption through manipulated external calls.
Likely Case
Contracts may produce incorrect results or unexpected behavior when interacting with external contracts, potentially causing transaction failures or minor financial discrepancies.
If Mitigated
With proper input validation and contract auditing, the risk is reduced to occasional unexpected behavior rather than critical exploitation.
🎯 Exploit Status
Exploitation requires understanding of smart contract interactions and Vyper compilation. No public proof-of-concept has been identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.3.4
Vendor Advisory: https://github.com/vyperlang/vyper/security/advisories/GHSA-4v9q-cgpw-cf38
Restart Required: No
Instructions:
1. Update Vyper to version 0.3.4 or later using pip: pip install vyper>=0.3.4
2. Recompile all existing Vyper contracts with the updated version
3. Redeploy affected smart contracts to blockchain networks
🔧 Temporary Workarounds
Avoid external calls without return values
allModify contracts to avoid making external calls that don't expect return values, or restructure contract logic to minimize such calls.
🧯 If You Can't Patch
- Audit all Vyper contracts for external calls without return values and manually verify logic correctness
- Implement additional contract-level validation and monitoring for unexpected behavior in production
🔍 How to Verify
Check if Vulnerable:
Check Vyper version with: vyper --version. If version is less than 0.3.4, the system is vulnerable.Check Version:
vyper --versionVerify Fix Applied:
Verify vyper --version shows 0.3.4 or higher, and test contract compilation with known vulnerable patterns.📡 Detection & Monitoring
Log Indicators:
- Unusual contract execution patterns
- Failed transactions with external calls
- Unexpected contract state changes
Network Indicators:
- Abnormal gas consumption patterns during external calls
- Multiple identical external calls in single transactions
SIEM Query:
Not applicable for blockchain environments; monitor transaction logs for repeated external contract calls🔗 References
- https://github.com/vyperlang/vyper/commit/6b4d8ff185de071252feaa1c319712b2d6577f8d
- https://github.com/vyperlang/vyper/security/advisories/GHSA-4v9q-cgpw-cf38
- https://github.com/vyperlang/vyper/commit/6b4d8ff185de071252feaa1c319712b2d6577f8d
- https://github.com/vyperlang/vyper/security/advisories/GHSA-4v9q-cgpw-cf38
