Symbol blockchain network upgrade

Summary

On 23 September 2025, the official Symbol blockchain X account （@thesymbolchain）announced a significant network upgrade.

This upgrade is scheduled to occur at block height 4,759,100, which is estimated to be on 25 September at 11:30 PM UTC.

The upgrade addresses a potential attack vector within the Symbol network and encourages node operators to implement the update promptly.

Upgrade Details

This network upgrade addresses a potential attack vector by fixing a bug that could cause aggregate transaction hashes to become non-unique under specific conditions. It also incorporates updated dependency libraries (CPPZMQ 4.11.0, RocksDB 10.5.1 and OpenSSL 3.5.2), thereby enhancing the network's overall stability and security. Additionally, Rest Gateway version 2.5.1 introduces support for aggregate transaction v3 and resolves an issue involving the missing maxFee property in WebSocket transactions. As these updates are BREAKING FORK, node operators must undertake preparatory work beforehand.

Catapult Client v.1.0.3.9
- Fixed:(BREAKING FORK) fix aggregate transaction hash bug where the aggregate transaction hashes were not unique in certain circumstances.
Rest Gateway v2.5.1
- Fixed:WebSocket transaction is missing the maxFee property, which was getting dropped.

Information for Developers

Updates are recommended for versions 3.3.0 of the JavaScript and Python SDKs, version 2.0.6 of the legacy TypeScript/JavaScript SDK, and version 1.0.4 of the Java SDK. These updates are intended to ensure compatibility with decentralised applications (dApps). Users are advised to release their applications once the target block height has been reached.

Additionally, updated versions of the Node Setup Tools, Symbol-Bootstrap (version 1.1.12) and Symbol-Shoestring (version 0.2.2), have been released on GitHub to facilitate swift upgrades.

Impact and Countermeasures

This upgrade significantly improves the security of the Symbol network and addresses potential attack vector. The bug, which under specific conditions could result in non-unique aggregate transaction hashes, could have enabled malicious attackers to disrupt the network. Correcting this issue improves the network's reliability.

Continued platform stability will contribute to business continuity for enterprise users. However, node operators and developers who neglect updates risk being forked out of the network.

As the upgrade time is based on block height, the precise timing may vary depending on the network's progress. For the latest information, we recommend checking the Symbol blockchain's official X account （@thesymbolchain）or the Symbol Community Web site.