Arbitrum Security Council Pauses New Stylus Deployments in Emergency Upgrade

The Arbitrum Security Council executed an emergency upgrade on October 2, 2026, at 11:30 EST, effectively freezing all new Stylus contract activations across both Arbitrum One and Nova. The action serves as a preemptive measure to prevent the deployment of unpatched WebAssembly programs that could potentially trigger denial-of-service vectors.

While the pause prevents new launches, existing Stylus contracts remain fully operational and can still be renewed. The identified vulnerabilities are related to network liveness rather than the safety of user funds, and the foundation noted that previous ArbOS patches had already addressed related issues.

In addition to the Stylus pause, the upgrade introduced a new permissionless guard to the BoLD one-step proof mechanism on Arbitrum One. This safeguard is designed to protect against potential soundness issues within the dispute resolution system. If the system were to accept contradictory proofs, the guard allows for the pausing of settlements, which could result in delays for unconfirmed withdrawals.

Stylus allows developers to build smart contracts using languages such as Rust and C++ while maintaining EVM compatibility. The current restriction on new activations will remain in place until the Arbitrum Foundation and the ArbitrumDAO determine a path forward for resuming deployments.

The use of emergency powers by the Security Council highlights a proactive approach to network security, prioritizing immediate risk mitigation over the standard governance process. The Arbitrum Foundation stated that this action is part of ongoing efforts to maintain the integrity of the network.