👮
Contract Cops
  • Mastering Ethereum Book
    • What is ethereum?
    • Tokens
    • Oracles
    • Decenralized Applications(DApps)
    • The Ethereum virtual machine
    • Ethereum basics
    • Ethereum clients
    • Cryptography
    • Wallets
    • Transactions
    • Chapter 7 - Smart Contracts & Solidity
    • Side Notes
      • Tokens
      • Smart Contracts and Solidity
  • Cryptography
    • Ethereum Cryptography - Cheatsheet
    • Assymetric vs symmetric cryptography
    • ECDSA vs RSA
    • Elliptic curves and ECDSA
    • Sha-256 Example
    • Sha-256
    • What are the different steps in SHA-256?
  • Ethereum Blocks
    • Block Headers
  • Learning Solidity
    • Storage vs memory
    • Upgradeable contracts
      • Proxy pattern in smart contracts
  • PoS
    • Proof of stake
  • PoW
    • PoW
  • Tokens
    • ERC-1155
    • ERC20
  • Cryptonomics
    • Automated market makers
    • Collateral Tokens
    • Collateralized Stablecoin
    • Fiat currency
    • Liquidity pool
    • Open Position: Meaning and Risk in Trading
    • Slippage
    • Spot price
  • Common Attack Vectors
    • Checking access control
    • Access control issues on critical functions
    • Account Existence Check for low level calls
    • Account Existence Check
    • Common attacks with contract/EOA addresses
    • Arithmetic under/overflow
    • Assert Attack
    • Assert require revert
    • Assert Violation
    • Bad Interface DOS
    • Bad pragma and compiler
    • Block Timestamp Manipulation
    • Bypassing contract check
    • Code With No Effects
    • Code size check vulnerability
    • Constructors with Care
    • Default Visibilities
    • Delegatecall
    • Delegatecall
    • Denial of Service (DoS)
    • DoS with block gas limit
    • Entropy Illusion
    • External contract referencing
    • Flash Loan Attack
    • Floating Point and Precision
    • Function selector abuse
    • Function selector abuse
    • Smart contract gas griefing
    • Hash collision parameters
    • Hash Collisions With Multiple Variable Length Arguments
    • Imprecise arithmetic
    • Improper Array Deletion
    • Incorrect array deletion
    • Incorrect interface
    • Insufficient Gas Griefing
    • Loop through long arrays
    • Message call with hardcoded gas amount
    • Not enough gas for ether transfer
    • Precision Loss in Calculations
    • Oracle Manipulation
    • Public Burn Function
    • Read-only reentrancy
    • Race Conditions/Front Running
    • Reentrancy Attacks
    • Reentrancy
    • Requirement Violation
    • Right-To-Left-Override control character (U+202E)
    • Shadowing State Variables
    • Short Address / Parameter attack
    • Signature Malleability
    • Signature Replay
    • Transaction Order Dependence
    • Tx.Origin Authentication
    • Unchecked CALL Return Values
    • Unexpected ether
    • Uninitialized Storage Pointers
    • Unsafe Ownership Transfer
  • EIP's
    • EIP155
    • EIP55
  • PoW
    • Ethash
    • Scrypt - RFC 7914
  • Questions for self evaluation
    • Questions 23/04/2023 (Nr: 84)
    • Usability guide for questions
  • Frequently asked questions
    • What is the difference between transaction and message?
    • What is the use of a interface or function without implementation?
  • UsefulResources
Powered by GitBook
On this page
  • Vulnerability examples
  • Prevention
  1. Common Attack Vectors

Shadowing State Variables

PreviousRight-To-Left-Override control character (U+202E)NextShort Address / Parameter attack

Last updated 2 years ago

Solidity allows for ambiguous naming of state variables when inheritance is used.

In a nutshell, the vulnerability occurs when the same state variable is declared in two places in contracts.

Example:

Contract A with a variable x could inherit contract B that also has a state variable x defined.

This is certainly a problem.

This would result in two separate versions of x, one of them being accessed from contract A and the other one from contract B. In more complex contract systems this condition could go unnoticed and subsequently lead to security issues.

Shadowing state variables can also occur within a single contract when there are multiple definitions on the contract and function level.

Vulnerability examples

Prevention

Review storage variable layouts for your contract systems carefully and remove any ambiguities. Always check for compiler warnings as they can flag the issue within a single contract.

Alt text
Alt text