EIP-1153 Transient Storage Security Traps: How a Gas Optimization Killed SIR.trading and What Your Reentrancy Guard Is Missing

EIP-1153 introduced TSTORE/TLOAD opcodes as gas-efficient alternatives to SSTORE/SLOAD, but their mid-transaction persistence across internal calls, callbacks, and reentrant calls creates critical security gaps. The SIR.trading protocol lost $355K in March 2025 due to an uncleared transient storage slot, and the low 100-gas cost of TSTORE breaks the long-standing assumption that 2,300 gas stipends prevent reentrancy attacks. Developers treating transient storage as a simple cheap replacement for persistent storage risk exposing contracts to novel attack vectors including low-gas reentrancy and cross-contract state coordination.