---
id: "CVE-2026-86065"
kind: "vulnerability"
aliases: ["CVE-2026-86065", "GHSA-4fwh-wrm6-97xm", "GO-2026-6581"]
title: "Klever-Go: Unauthenticated WebSocket /subscribe: no read-size limit, no connection cap, permissive origin -> remote node memory/goroutine exhaustion (DoS) in github.com/klever-io/klever-go"
severity: "high"
cvss: 7.5
epss: 0.0035
exploited: false
status: "open"
category: "package"
products: [{"name": "github.com/klever-io/klever-go", "fixed": ["1.7.20"], "affected": "< 1.7.20", "ecosystem": "go"}]
ecosystems: ["go"]
tags: ["blockchain", "go", "klever-go", "klever-node", "package"]
not_affected_if: ["api-port-not-exposed", "version-1.7.20-or-later"]
published_at: "2026-09-23T20:17:20+00:00"
first_seen_at: "2026-10-23T19:13:08+00:00"
updated_at: "2026-10-23T19:56:16+00:00"
sources: [{"source": "govuln", "url": "https://pkg.go.dev/vuln/GO-2026-6581", "first_seen_at": "2026-10-23T19:13:08+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-86065", "first_seen_at": "2026-10-23T19:13:43+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-86065", "first_seen_at": "2026-10-23T19:35:23+00:00"}]
---

# Klever-Go: Unauthenticated WebSocket /subscribe: no read-size limit, no connection cap, permissive origin -> remote node memory/goroutine exhaustion (DoS) in github.com/klever-io/klever-go

Klever-Go nodes before 1.7.20 expose an unauthenticated /subscribe WebSocket endpoint with no message size limit, no connection cap, and permissive origin checks. An attacker can exhaust memory or goroutines on the node, crashing it and interrupting P2P and consensus participation.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- go:github.com/klever-io/klever-go affected < 1.7.20 fixed 1.7.20

## How to check

Check whether the node's go.mod or binary pins github.com/klever-io/klever-go below 1.7.20 (for example: go list -m github.com/klever-io/klever-go).
Check whether the REST/WebSocket API port is reachable from untrusted networks and whether GET /subscribe responds to WebSocket upgrades.

## Fix

Upgrade github.com/klever-io/klever-go to 1.7.20 or later and restart the node.
Until upgraded, restrict network access to the node's API port to trusted addresses.

## Timeline

- 2026-10-23T19:13:08+00:00 govuln https://pkg.go.dev/vuln/GO-2026-6581
- 2026-10-23T19:13:43+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-86065
- 2026-10-23T19:35:23+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-86065

## From the sources

Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.20, the default-open GET /subscribe endpoint in network/api/websocket/routes.go accepts unauthenticated WebSocket clients with permissive origin handling, does not call SetReadLimit to bound message size, and has no live-connection cap. SocketHub.HandleClientInsertion also accepts an unbounded address list that grows addressSubscription, and client.loopIn continues reading without a size limit, allowing one client to grow subscription maps or many clients to retain goroutines, buffered channels, and descriptors. The global HTTP request throttler does not count upgraded live WebSocket connections. Because the REST and WebSocket API runs in the node process, memory or scheduler exhaustion can crash the node and interrupt P2P and consensus participation. This issue is fixed in version 1.7.20.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_