Storage Collision Vulnerability

Storage collision vulnerability occurs in proxy patterns when the implementation contract overwrites variables stored in the proxy contract. Because the proxy and implementation share the same storage slot context during execution, if the memory layout is not carefully managed, a new implementation might write data into a slot already used by the proxy.

This can corrupt critical state variables, such as owner addresses or balances, leading to unpredictable behavior or total loss of control. Developers prevent this by using specific storage patterns, such as unstructured storage or EIP-1967, which reserves specific, non-colliding slots for proxy variables.

Maintaining a consistent storage structure across different versions of the implementation is essential for security. Failure to do so can result in permanent loss of access to the contract state.

This risk is a primary concern for any upgradeable DeFi instrument.