Arbitrum Halts New Stylus Activations Over Security Concerns
Arbitrum’s Security Council has temporarily halted new Stylus contract activations on Arbitrum One and Arbitrum Nova as a precautionary measure. The pause, effective October 2, targets hand-crafted WebAssembly (WASM) programs that could threaten the network’s liveness. According to the Arbitrum Foundation, the action applies only to the activation step, meaning existing contracts remain operational until their expiration.
The freeze prevents developers from activating new Stylus contracts or renewing expired ones, but Solidity and EVM contract deployments are unaffected. Stylus, introduced in September 2024, allows developers to write Ethereum-compatible smart contracts in languages like Rust, compiled to WASM. The concern arises from potential denial-of-service risks posed by custom WASM programs, though no user funds have been compromised.
The Security Council enacted the pause by raising the Stylus activation gas requirement to an impractical level, a change that did not require an ArbOS upgrade. The foundation emphasized its continued confidence in Stylus and plans to reopen activations while restricting custom WASM programs. The timeline for lifting the pause remains undetermined.
The emergency action also introduced a safeguard for BoLD’s one-step proofs on Arbitrum One, which could delay unconfirmed withdrawals if conflicting proofs are accepted. Transactions would continue processing normally during any suspension. All active Stylus contracts on Arbitrum One were renewed through the ArbOS 61 upgrade, ensuring none expire before August 20, 2027.