Terra Classic Announces Mandatory Security Upgrade on September 24
Terra Classic is preparing for an important network upgrade to fix a critical security vulnerability. The mandatory upgrade to v4.0.1-patch.3 is scheduled for September 24, 2026, several days before details of the vulnerability are expected to become public.
The upgrade will take place when the Terra Classic blockchain reaches block 30,544,730. The current estimate is Thursday, September 24, at 15:00 UTC.
The upgrade is mainly aimed at validators and infrastructure operators responsible for keeping the Terra Classic network running.
Why Is Terra Classic Upgrading?
The upgrade is being carried out because a critical security vulnerability has been discovered in components used by the Terra Classic smart contract system.
The affected components are called wasmd and wasmvm. These are important parts of the software that supports smart contracts on the network.
Cosmos Labs is expected to publicly disclose the vulnerability details on September 28, 2026, at 14:00 UTC.
Before that disclosure, Terra Classic developers have prepared a patched version of the network software called v4.0.1-patch.3.
When Will the Upgrade Happen?
| Upgrade Detail | Information |
|---|---|
| Network | Terra Classic |
| Software Version | v4.0.1-patch.3 |
| Upgrade Block | 30,544,730 |
| Estimated Date | September 24, 2026 |
| Estimated Time | 15:00 UTC |
| Reason | Critical security fix |
The September 24 time is an estimate based on recent block production. The actual timing may vary, so validators and node operators should monitor the blockchain height rather than rely only on the estimated time.
Who Needs to Upgrade?
The upgrade applies to infrastructure running the Terra Classic columbus-5 network, including:
- Validators
- Node operators
- RPC providers
- Exchanges
- IBC relayers
- Blockchain explorers
- Bridges
- Wallet infrastructure
Nodes that have not been upgraded will stop at block 30,544,730 and will not be able to continue following the network until they are running the required software.
Validators using a Validator as a Service provider should check with their provider if they are unsure whether the upgrade will be handled for them.
What Does This Mean for LUNC Holders?
For most LUNC holders, no manual software upgrade is required. Users holding LUNC in a personal wallet should continue using their wallet normally unless their wallet provider publishes separate instructions.
Users holding LUNC on exchanges should follow any announcements from their exchange if deposits or withdrawals are temporarily affected around the upgrade.
What Happens at Block 30,544,730?
When Terra Classic reaches block 30,544,730, the network will temporarily stop producing new blocks as part of the planned upgrade.
Nodes running the older software will stop at the upgrade height because they do not have the required version.
Validators running v4.0.1-patch.3 will then restart their nodes and continue operating on the upgraded network.
Block production will resume once validators representing more than two thirds of the network voting power are running the new version.
Validators that have not upgraded may miss blocks while offline and could face the usual downtime related slashing rules.
Does the Upgrade Change LUNC?
The upgrade does not introduce changes to the LUNC token economics or network parameters.
According to the release information, there is no state migration, no new store and no parameter change.
The purpose of the upgrade is to apply the security fix and ensure Terra Classic continues operating with the patched software.
How Should Validators Prepare?
Validators and node operators should download the new v4.0.1-patch.3 release before the scheduled upgrade and verify the published checksum.
The release provides binaries for different Linux architectures, including x86_64 and ARM64. Operators should use the version that matches their system.
After installation, the software version should report:
terrad version
4.0.1-patch.3Operators should not replace the running binary before the scheduled upgrade height. Running the new binary too early can cause the node to stop before the upgrade is triggered.
The official release also warns against using –unsafe-skip-upgrades. Skipping the upgrade would leave the node on vulnerable software and could prevent it from following the upgraded network.
Why the Upgrade Is Being Completed Before September 28
The timing of the upgrade is directly connected to the planned public disclosure of the vulnerability.
Cosmos Labs is expected to publish the vulnerability details on September 28. Terra Classic is therefore scheduled to upgrade several days earlier, giving network operators time to move to the patched software.
This allows the network to address the security issue before the attack vector becomes publicly available.
Official Terra Classic Release
The complete release notes, binaries, checksums and technical instructions are available through the official Terra Classic Core repository.
Release: Terra Classic Core v4.0.1-patch.3
Bottom Line
Terra Classic is preparing for a mandatory security upgrade to v4.0.1-patch.3 at block 30,544,730, currently estimated for September 24, 2026.
The upgrade addresses a critical security vulnerability before its details are expected to become public on September 28. Validators and infrastructure operators need to prepare for the upgrade, while most regular LUNC holders do not need to take any direct action.
