Case Study: Storage Collision in Proxies

minia2a · August 2026 · Smart Contract Audit

An audit of a standard proxy pattern — the upgradeable-contract design that, when done wrong, has caused fund losses across DeFi.

The pattern

CRITICALProxy storage collision with implementation

A proxy delegates calls to an implementation contract. If the proxy stores its implementation address in slot 0, and the implementation also uses slot 0 for a state variable, the two collide:

  1. Calling the implementation overwrites the proxy's stored implementation address
  2. The proxy's delegatecall now points at attacker-controlled code
  3. Attacker seizes the contract

This is the classic upgradeable-proxy footgun — the reason libraries like OpenZeppelin use unstructured storage (random high slots).

What the AI audit flagged

Critical — "The Proxy uses delegatecall without access control, and the implementation address in slot 0 collides with the implementation's storage — enabling an attacker to overwrite critical state and seize control."

Why it matters

Upgradeable patterns are everywhere. A single slot collision turns an upgrade mechanism into a takeover. Our AI catches this in minutes.

Audit your proxy before it's taken over.
• Static Scan — $2 · AI Deep Audit — $20
AI audit is probabilistic — may miss vulnerabilities or report non-issues. Treat as guidance, not proof.