CVE-2026-58208
Description
A flaw was found in NATS Server. An unauthenticated client with access to the WebSocket listener could exploit a vulnerability where requests for the MQTT-over-WebSocket path were incorrectly routed into MQTT handling, even when MQTT was not configured. This allowed the client to access uninitialized MQTT state, leading to a server process crash. This can result in a Denial of Service (DoS) for the NATS Server.
Statement
This Moderate flaw in NATS Server allows an unauthenticated remote attacker to cause a denial of service. The vulnerability arises from incorrect routing of WebSocket requests to uninitialized MQTT handling, even when MQTT is not configured, leading to a server crash. This impacts the availability of NATS Server deployments that expose a WebSocket listener, as it does not require specific MQTT configuration to exploit.
Mitigation
To mitigate this issue, restrict network access to the NATS Server's WebSocket listener to trusted clients only using firewall rules. If the WebSocket listener is not required, it can be disabled in the NATS Server configuration. Disabling the WebSocket listener may impact services that rely on WebSocket connectivity to the NATS Server. After making configuration changes, ensure to restart the NATS Server process for the changes to take effect.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.8 | 7.5 | 6.8 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | High |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Changed | Unchanged | Changed |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the uninitialized pointer is used in a read operation, an attacker might be able to read sensitive portions of memory.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the uninitialized pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the uninitialized pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
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