The Arbitrum Security Council completed an emergency action on Oct. 2 that temporarily disables new Stylus contract activations on Arbitrum One and Nova. The council raised the activation gas requirement to 264−1, effectively making new activations infeasible, according to an Arbitrum Foundation Forum post published at 3:30 p.m. ET.
Arbitrum described the measure as a precaution against sophisticated attacks using hand-crafted WebAssembly programs. It said the potential attacks may be AI-assisted and could degrade chain performance or create denial-of-service conditions; the network reported no known theft of user funds.
Emergency gas threshold halts new Stylus activations
The emergency change does not remove Stylus from the network, but it blocks several paths requiring a fresh activation. Those include new Stylus contracts, reactivation of expired contracts and application updates that require activation.
Stylus is Arbitrum’s environment for deploying programs that can use WebAssembly-based languages alongside Ethereum-compatible smart contracts. By setting the activation requirement at the maximum stated threshold, the council has temporarily stopped developers from bringing those new or updated Stylus applications into operation.
The forum notice did not provide a date for restoring normal activation conditions or describe a separate governance timetable for the change.
Hand-crafted WebAssembly prompted the precautionary pause
Arbitrum said its concern centers on specially constructed, hand-crafted WebAssembly programs, not a confirmed exploit involving user assets or known user-fund theft. In the network’s assessment, such programs could strain chain performance or trigger a denial-of-service scenario. The precautionary action is intended to prevent potentially risky new Stylus code from being activated while leaving already-active contracts and existing operations in place, rather than shutting down Stylus activity generally.
Active contracts and EVM deployments remain operational
Already-active Stylus contracts continue to operate under the emergency action. Solidity and other EVM deployment and execution are also unaffected, Arbitrum said, limiting the direct restriction to the Stylus activation process.
Separately, the action added a permissionless guard for Arbitrum One’s BoLD one-step proof system. The safeguard allows settlement to Ethereum to be paused if conflicting proofs are accepted, according to Crypto Briefing.
That additional measure addresses the settlement path rather than the activation restriction itself, adding a mechanism to halt settlement in the specified conflicting-proof scenario.
