The execution of smart contracts on the Ethereum blockchain consumes gas paid for by users submitting contracts’ invocation requests. A contract execution proceeds as long as the users dedicate enough gas, within the limit set by Ethereum. If insufficient gas is provided, the contract execution halts and changes made during execution get reverted. Unfortunately, contracts may contain code patterns that increase execution cost, causing the contracts to run out of gas. These patterns can be manipulated by malicious attackers to induce unwanted behavior in the targeted victim contracts, e.g., Denial-of-Service (DoS) attacks. We call these gas-related vulnerabilities. We propose eTainter, a static analyzer for detecting gas-related vulnerabilities based on taint tracking in the bytecode of smart contracts. We evaluate eTainter by comparing it with the prior work, MadMax, on a dataset of annotated contracts. The results show that eTainter outperforms MadMax in both precision and recall, and that eTainter has a precision of 90% based on manual inspection. We also use eTainter to perform large-scale analysis of 60,612 real-world contracts on the Ethereum blockchain. We find that gas-related vulnerabilities exist in 2,763 of these contracts, and that eTainter analyzes a contract in eight seconds, on average.