Polygon's Emergency Hard Fork Involves Transaction Reversal

Technical Failure Analysis

Polygon’s Proof-of-Stake (PoS) network suffered a critical software bug affecting two core components: Bor, the block production layer, and Heimdall, the consensus mechanism. The issue, which originated from a faulty validator proposal, caused some Bor and RPC nodes to fall out of sync, disrupting the creation of “milestones” — Polygon’s term for fast local finality on the Layer 2 network. While block production continued uninterrupted, transaction finality was delayed by 10-15 minutes, and some validators and RPC providers were forced to roll back the most recently finalized block to resynchronize.

The outage has had a significant impact on Polygon's ecosystem:

• Polygonscan, the network's main block explorer, has not shown any block updates for over five hours, raising concerns among users.

• Several exchanges and DeFi protocols, including multi-chain wallet TokenPocket, have temporarily suspended Polygon-based transactions.

• Traders on platforms like Polymarket have warned of the possibility of trade reversals during the outage.

The Polygon Foundation confirmed the issue via its status page and X, noting that while the blockchain remained operational, the bug disrupted RPC services, which are critical for applications interacting with the network. By 3 p.m. UTC, the team had deployed a hard fork, releasing Bor v2.2.11-beta2 and Heimdall v0.3.1 updates, which removed the bug from the node database and restored consensus and finality.

This incident is not the first time Polygon has experienced network instability. The network went down an hour after a validator exit caused a bug in Heimdall, shortly after the Bhilai hard fork on July 1, which upgraded throughput to 1,000 transactions per second (TPS) and integrated Ethereum’s Pectra Ethereum Improvement Proposal (EIP). The recurring issues so soon after a major upgrade have raised questions about the robustness of Polygon’s recent architectural changes, particularly the transition to Heimdall v2 with CometBFT for faster finality.

Technical Response from Polygon

Polygon Foundation's response was swift and consistent:

• Engineers identified a bug in Bor and Heimdall, pointing to a faulty milestone causing node desynchronization.

• Hard Fork Deployment: At 3pm UTC, Bor v2.2.11-beta2 and Heimdall v0.3.1 updates were deployed, removing the problematic milestone from the node database.

• After the fork, the team confirmed that checkpoints, milestones, and state synchronization are working properly, with ongoing monitoring to ensure stability.

Polygon's block production layer remained operational throughout the outage, ensuring that on-chain transactions did not completely stop. The team also worked with Polygonscan to switch to working nodes, resolving the block explorer pause. By 8:52 UTC, the Foundation reported that checkpoint completion had been restored within 15 minutes and real-time block production could be monitored via alternate links.

Evaluation and Conclusion

The Polygon network’s emergency hard fork on September 10, 2025, successfully fixed a critical bug that disrupted transaction finality, but the outage left lingering questions about the platform’s reliability. While the Polygon Foundation’s swift response mitigated the damage, the incident highlighted the challenges of scaling blockchain networks while maintaining stability.

Disclaimer: The information presented in this article is the author's personal opinion on the cryptocurrency field. It is not intended to be financial or investment advice. Any investment decision should be based on careful consideration of your personal portfolio and risk tolerance. The views expressed in the article do not represent the official position of the platform. We recommend that readers conduct their own research and consult with a professional before making any investment decisions.