BNB Chain activated the Pasteur hard fork on BNB Smart Chain mainnet at 02:30 UTC on Aug. 25, introducing three changes focused on bridge security, validator authorization and block capacity.
Summary
- BNB Chain activated Pasteur on BSC mainnet at 02:30 UTC on August 25, 2026, successfully.
- Three proposals strengthen bridge verification, validator authorization and block construction without shortening block times further.
- BEP-682 rejects duplicate validators during cross-chain light-block checks, protecting genuine supermajority approval requirements onchain now.
- QANet benchmarks increased throughput 88% from 1,237 to 2,324 transactions per second under controlled conditions.
- Node operators needed client version 1.7.7 and removal of EnableBAL before mainnet activation began Tuesday.
The network confirmed that Pasteur was live following its scheduled activation. BSC continued producing blocks at its existing 450-millisecond interval, with no major disruption publicly reported immediately after the upgrade.
Pasteur combines BEP-682, BEP-695 and BEP-675 under the broader BEP-673 upgrade plan. The changes had operated on BSC’s Chapel testnet since July 21 before reaching mainnet.
BNB Chain Pasteur strengthens bridge verification
BEP-682 changes how BSC verifies light blocks submitted through cross-chain infrastructure. Before Pasteur, the verification process did not explicitly reject duplicate entries in a submitted validator list.
A crafted request could therefore include the same validator more than once. Counting those entries separately risked making a bridge approval appear to have support from more independent validators than it actually did.
Pasteur rejects repeated validator entries before calculating whether the required voting threshold has been reached. Each approval must now come from a distinct validator for the light block to satisfy the supermajority requirement.
BNB Chain did not report that attackers had exploited the flaw or attributed any previous asset losses to it. The change is a preventive correction to bridge verification rather than a response to a disclosed theft.
Cross-chain infrastructure remains a major security concern across decentralized networks. In related coverage, bridge attacks have caused billions of dollars in cumulative losses through compromised keys, contract flaws and weak message verification.
Old validator keys lose their authority
BEP-695 closes gaps involving validator key rotation, penalties and governance. When a validator replaces its operator key, the previous key now loses its management rights.
The proposal also prevents validators from escaping pending penalties by rotating their keys. Slashing and removal processes remain attached to the validator rather than disappearing when its operator address changes.
Pasteur further blocks restricted addresses from using offchain signatures to participate in governance. BNB Chain already prevented blacklisted addresses from voting directly, but those accounts could potentially sign votes and have another address submit them.
The updated governance contracts check the original signer before counting a delegated vote. If that signer is restricted, the vote is rejected regardless of which account submits it.
New block route reduces repeated execution
BEP-675 introduces an optional route for specialist builders to submit blocks they have already executed. Validators check the proposed block against consensus rules, sign it and broadcast it before completing full execution verification.
The earlier route required both the builder and validator to execute the transactions before the validator signed. That duplication consumed part of BSC’s short block window and could leave blocks below their maximum capacity during periods of heavy demand.
Builders can continue using the previous process. The new route must be enabled through the network’s remote procedure call interface, giving participants time to integrate it.
BNB Chain said the route could fit more transactions into each block, but its published performance figures came from controlled testing rather than mainnet activity.
Tests on QANet, an internal environment designed to reflect geographically distributed validators, increased throughput from 1,237 to 2,324 transactions per second. Average gas consumption per block rose from 46.35 million to 84.15 million while the 100-million gas limit remained unchanged.
Mainnet data will test the 88% capacity gain
Pasteur does not increase the block gas limit or reduce the 450-millisecond block interval introduced by the Fermi upgrade. Its capacity gains depend on builders adopting BEP-675 and submitting fuller blocks.
BNB Chain required node operators to install client version 1.7.7 before activation. Operators also needed to remove the deprecated EnableBAL field because leaving it in the configuration file would prevent the updated client from starting.
As previously reported, BNB Chain warned operators to complete the mandatory Pasteur update before the fork. Operators running incompatible software risked falling out of sync with mainnet.
The next evidence will come from live block utilization, transaction throughput, missed-block rates and validator performance. Those measurements will show whether the QANet capacity improvement carries over to sustained mainnet demand.
