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

> Unauthenticated WebSocket connections in Klever-Go allow remote attackers to exhaust node memory and goroutines, causing a denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 23 Sep 2026
- **Updated:** 29 Sep 2026
- **Also known as:** GHSA-4fwh-wrm6-97xm, GO-2026-6581

## What is CVE-2026-86065?

CVE-2026-86065 is a high-severity denial of service vulnerability in klever-io klever-go, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-86065?

3 open source packages ship an affected version, including github.com/klever-io/klever-go.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/klever-io/klever-go` | Go | All versions | 1.7.20 |
| `github.com/klever-io/klever-go` | Go | All versions | 1.7.20 |
| `github.com/klever-io/klever-go` | Go | All versions | 1.7.20 |

## How do I fix CVE-2026-86065?

Upgrade github.com/klever-io/klever-go to 1.7.20 or later.

## Is CVE-2026-86065 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-86065 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-86065 and fix it if it is affected.

What it is: CVE-2026-86065 is a high-severity denial of service vulnerability in klever-io klever-go, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-86065 exists.

Affected packages and fixed versions:
- github.com/klever-io/klever-go (Go): affected all versions; fixed in 1.7.20
- github.com/klever-io/klever-go (Go): affected all versions; fixed in 1.7.20
- github.com/klever-io/klever-go (Go): affected all versions; fixed in 1.7.20

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-86065/ (Markdown: https://insights.sbomify.com/CVE-2026-86065/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-86065
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-86065
- OSV: https://osv.dev/vulnerability/CVE-2026-86065

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-86065/
Summaries are generated and may contain mistakes; the official description above is the record.