# CVE-2026-58208: NATS Server: MQTT-over-WebSocket Path Can Crash WebSocket-Only JetStream Servers Before MQTT Is Enabled

> Unauthenticated attackers can crash NATS Server via WebSocket requests to MQTT paths, even when MQTT is disabled, requiring an upgrade to fix.

- **Severity:** Medium 6.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/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:** 8 Jul 2026
- **Updated:** 9 Jul 2026
- **Also known as:** AZL-92247, DEBIAN-CVE-2026-58208, GHSA-p957-7v2w-g93g, UBUNTU-CVE-2026-58208

## What is CVE-2026-58208?

CVE-2026-58208 is a medium-severity denial of service vulnerability in nats-io nats-server, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, a WebSocket listener could route requests for the MQTT-over-WebSocket path into MQTT handling even when MQTT was not configured, allowing an unauthenticated client with access to the WebSocket listener to reach uninitialized MQTT state and crash the server process. This issue is fixed in versions 2.14.3 and 2.12.12.

Weakness: CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2026-58208?

It affects 1 product.


Products: Linuxfoundation Nats-Server.

## How do I fix CVE-2026-58208?

Upgrade to a fixed version.

## Is CVE-2026-58208 being exploited?

There is no known exploitation of CVE-2026-58208 in the wild and no public exploit code.

## Other vulnerabilities in nats-io nats-server

- [CVE-2022-28357](https://insights.sbomify.com/CVE-2022-28357/): NATS nats-server allows directory traversal via unintended path to a management action (critical 9.8)
- [CVE-2026-58253](https://insights.sbomify.com/CVE-2026-58253/): NATS Server: Route API Auth Bypass (high 8.8)
- [CVE-2022-24450](https://insights.sbomify.com/CVE-2022-24450/): Incorrect Authorization in NATS nats-server (high 8.8)
- [CVE-2026-33216](https://insights.sbomify.com/CVE-2026-33216/): NATS has MQTT plaintext password disclosure (high 8.6)
- [CVE-2026-58207](https://insights.sbomify.com/CVE-2026-58207/): NATS Server: Remote crash via integer overflow in Connz pagination (high 7.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-58208 and fix it if it is affected.

What it is: CVE-2026-58208 is a medium-severity denial of service vulnerability in nats-io nats-server, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-58208 in the wild and no public exploit code.

Affected product: nats-io nats-server. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-58208/ (Markdown: https://insights.sbomify.com/CVE-2026-58208/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-58208
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-58208
- OSV: https://osv.dev/vulnerability/CVE-2026-58208

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-58208/
Summaries are generated and may contain mistakes; the official description above is the record.