# Klever Blockchain Mainnet v1.7.21 🚨

**URL:** <https://forum.klever.org/t/klever-blockchain-mainnet-v1-7-21/4549>\
**Category:** News and Announcements\
**Tags:** kleverchain, validator, security\
**Created:** [September 23, 2026, 6:39pm UTC](https://forum.klever.org/t/klever-blockchain-mainnet-v1-7-21/4549 "2026-09-23T18:39:56Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Duka](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.klever.org/duka/32/415_2.png) [@Duka](https://forum.klever.org/u/Duka)\
**Post date:** [September 23, 2026, 6:39pm UTC](https://forum.klever.org/t/klever-blockchain-mainnet-v1-7-21/4549/1 "2026-09-23T18:39:56Z")

</div>

![image](https://europe1.discourse-cdn.com/flex013/uploads/klever/original/2X/6/61d8462b48697d1cddcde61689ef20e0e0123bc9.jpeg)

**Attention to all Validators, Node Maintainers, and Exchanges,**

This is a **mandatory** security announcement. Klever Blockchain has officially released version **v1.7.21** for the Mainnet. This is a critical security update that affects consensus rules, making it strictly mandatory for all operators to upgrade in order to maintain network synchronization.

**Nodes that have not been updated will fork from the main network, and the validator may get jailed.**

### 🛡 Update and Security Summary

Version v1.7.21 is a crucial milestone for the network, closing nine vulnerabilities reported through coordinated disclosure (7 High severity and 2 Medium severity). Furthermore, this release continues the remediation of security findings identified in the CertiK protocol audit (KLR series).

**Key highlights of this release include:**

- **Critical Security in KVM and Consensus:** Fixes for use-after-free and integer overflow vulnerabilities that could crash nodes or bypass gas limits during smart contract execution.
- **P2P and API Protection:** Hardening of direct-send streams to prevent memory exhaustion and bounding of long-lived WebSocket connections that could hold global API slots.
- **Staking and Marketplace:** A fix that preserves accrued KDA FPR rewards across a stake top-up, along with snapshotting marketplace referral addresses to prevent settlement failures.
- **New Fork Flags:** Introduction of two essential new fork flags (`fixAuditChangesV4` and `fixAuditChangesV5`) required to maintain consensus among nodes.

For a complete and detailed technical analysis of all fixes and improvements, we strongly recommend visiting the official GitHub link:🔗 **[Release Notes v1.7.21 on GitHub](https://github.com/klever-io/klever-go/releases/tag/v1.7.21)**

> _⚠ **IMPORTANT NOTICE:** Users who have already updated to the_ `v1.7.21-rc3` _version do not mandatorily need to perform this update._

### ⚙ Upgrade Instructions

The upgrade took place on epoch 6160 (Friday, 18 September 2026, 13:00:00 UTC) as v1.7.21-rc3.

Make sure to update your config files prior to updating the node (there are changes with the fork update in `enableEpochs.yaml`).

Please do the following:

**1. Download the new config:**

```bash
curl -k https://backup.mainnet.klever.org/config.mainnet.108.tar.gz | tar -xz -C ./node

```

**2. Download the new image version:**

```bash
docker pull kleverapp/klever-go:v1.7.21-0-gc8c88b0e

```

**3. Update the permissions of the database directories:**

```bash
chown -R 999 $(pwd)/node/config
chown -R 999 $(pwd)/node/db
chown -R 999 $(pwd)/node/logs

```

**4. Stop and remove your current node:**

```bash
docker stop klever-node && docker rm klever-node

```

**5. Run your node again:**

```bash
docker run -it -d --restart unless-stopped \
    --user "$(id -u):$(id -g)" \
    --name klever-node \
    -v $(pwd)/node/config:/opt/klever-blockchain/config/node \
    -v $(pwd)/node/db:/opt/klever-blockchain/db \
    -v $(pwd)/node/logs:/opt/klever-blockchain/logs \
    --network=host \
    --entrypoint=/usr/local/bin/validator \
    kleverapp/klever-go:v1.7.21-0-gc8c88b0e \
    '--log-save' '--use-log-view' '--rest-api-interface=0.0.0.0:8080'

```

🌐 **Important Notice for Proxy (Indexer) Users**

If you are also running the proxy (indexer), you **must** verify your `external.yaml` configuration:

- Ensure that `enable` is set to `true`.
- Ensure it is correctly pointing to both your node and your Elasticsearch instance.

**Ecosystem security is our top priority.** The integrity of the Klever Blockchain relies entirely on the technical diligence of our validators and exchange partners. Please perform this update immediately to protect your operations and ensure network health.