BNB Chain has activated the Pasteur hard fork on the BNB Smart Chain (BSC) mainnet. The upgrade bundles three improvement proposals under the umbrella designation BEP-673, aimed at closing security vulnerabilities in cross-chain bridges and validator governance while making block processing more efficient.

Ahead of activation, mainnet nodes were required to run client version 1.7.7, and operators were advised to remove the [Eth] EnableBAL parameter from config.toml to ensure compatibility. Several command-line interface flags have been deprecated or rendered inert in the process, including options tied to journal files, transaction pool overflow slots, and the fake-beacon family.

Pasteur builds on earlier network optimizations that reduced block times to 0.45 seconds and stabilized performance at that pace. Whereas previous hard forks concentrated primarily on speed, Pasteur prioritizes fuller use of existing capacity and the elimination of validator power retention mechanisms.

Bridge and Validator Security Fixes

BEP-682 patches a critical vulnerability in the bridge verification precompile at address 0x67, where duplicate validator signatures could previously be counted repeatedly toward the required threshold — potentially allowing cross-chain asset transfers to clear with fewer legitimate signers than mandated by protocol rules. Cross-chain bridges have historically ranked among the most exploited components in the industry, with 2022 attacks on Ronin Network, Wormhole, and BNB Chain's own Token Hub bridge each causing losses in the hundreds of millions of dollars — a track record that makes bridge verification logic a standing security priority across the sector.

BEP-695 standardizes post-rotation validator key management. It ensures that retired consensus keys immediately lose administrative privileges, maintains slash eviction status across key rotations, and closes a loophole in signature-based governance voting that had permitted blacklisted addresses to bypass restrictions applicable to direct votes. Because BSC's cross-chain transfers and governance votes both depend on signatures from its small, regularly rotating validator set, the lifecycle of retired keys directly affects who can move funds or cast protocol-level votes.

BNB Chain confirmed the activation in an official post on X:

Pasteur hardfork is now live on BSC Mainnet. The upgrade strengthens bridge, staking and governance security, while giving blocks more room to carry transactions at the same 450ms block time. Read the full upgrades pic.twitter.com/mTTnRb9PNk

— BNB Chain (@BNBCHAIN), August 25, 2026 (X post)

Performance Optimization and Builder Requirements

BEP-675 introduces the most significant structural change to block production by allowing builders to submit pre-executed blocks, eliminating the need for validators to rerun all transactions during the 450-millisecond block window. Under the previous architecture, builders and validators independently executed the same transaction set — a redundancy that consumed approximately 125 milliseconds of the critical path and frequently left blocks operating well below capacity. The division of labor echoes the proposer-builder separation that already routes a large share of Ethereum blocks through specialized external builders via MEV-Boost, though BNB Chain's pre-execution pathway is built into the protocol itself rather than layered on top through an out-of-protocol relay.

Testnet benchmarks conducted on QANet, which mirrors mainnet's cross-region validator topology, demonstrated that the optimization reduced validator processing time to 15 milliseconds. Throughput increased from 1,237 to 2,324 transactions per second while maintaining the existing gas limit and block interval, with average gas utilization improving from 46.35 million to 84.15 million per block.

The upgrade requires no migration for general developers or end users, who will benefit from increased block space availability during high-demand periods without changes to gas fees or daily operations. Block builders seeking to leverage the BEP-675 pathway must transition from fastnode to fullnode infrastructure, as they now assume responsibility for producing fully executed blocks. Legacy bidding mechanisms remain operational for those not immediately adopting the new flow.

The BEP-675 initiative forms part of BNB Chain's second-half 2026 roadmap, which targets doubling mainnet throughput as an intermediate step toward a long-term tenfold capacity improvement across the ecosystem. The upgrade's real-world effect will be measurable on-chain, with mainnet gas utilization and transactions per second now directly comparable against the QANet benchmarks of 84.15 million gas per block and 2,324 TPS, and the pace of builder migration from fastnode to fullnode infrastructure serving as the other near-term indicator of adoption.