CVE-2026-33218

HIGH
2026-03-24 https://github.com/nats-io/nats-server
7.5
CVSS 3.1
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CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

3
Patch Released
Mar 31, 2026 - 21:13 nvd
Patch available
Analysis Generated
Mar 24, 2026 - 21:46 vuln.today
CVE Published
Mar 24, 2026 - 21:45 nvd
HIGH 7.5

Tags

Denial Of Service

Description

### Background NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing. The nats-server allows hub/spoke topologies using "leafnode" connections by other nats-servers. ### Problem Description A client which can connect to the leafnode port can crash the nats-server with a certain malformed message pre-authentication. ### Affected Versions Any version before v2.12.6 or v2.11.15 ### Workarounds 1. Disable leafnode support if not needed. 2. Restrict network connections to your leafnode port, if plausible without compromising the service offered. ### References * This document is canonically: <https://advisories.nats.io/CVE/secnote-2026-10.txt> * GHSA advisory: <https://github.com/nats-io/nats-server/security/advisories/GHSA-vprv-35vv-q339> * MITRE CVE entry: <https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-33218>

Analysis

A pre-authentication vulnerability in NATS.io nats-server allows unauthenticated attackers to crash the server by sending a specially crafted malformed message to the leafnode port. All versions of nats-server prior to v2.12.6 and v2.11.15 are affected. …

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Remediation

Within 24 hours: Inventory all nats-server deployments and confirm affected versions; assess business criticality of each instance. Within 7 days: Implement network segmentation to restrict leafnode port access to trusted internal networks only; enable detailed logging on NATS servers to detect exploitation attempts. …

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Priority Score

38
Low Medium High Critical
KEV: 0
EPSS: +0.1
CVSS: +38
POC: 0

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CVE-2026-33218 vulnerability details – vuln.today
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