nats-io nats-server up to 2.11.14/2.12.5 leafnode denial of service

Summaryinfo

A vulnerability was found in nats-io nats-server up to 2.11.14/2.12.5. It has been declared as problematic. This impacts an unknown function of the component leafnode Handler. Such manipulation leads to denial of service. This vulnerability is listed as CVE-2026-33218. The attack may be performed from remote. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in nats-io nats-server up to 2.11.14/2.12.5. It has been rated as problematic. Affected by this issue is some unknown processing of the component leafnode Handler. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability. CVE summarizes:

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, a client which can connect to the leafnode port can crash the nats-server with a certain malformed message pre-authentication. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable leafnode support if not needed or restrict network connections to the leafnode port, if plausible without compromising the service offered.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-33218. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1499.

The vulnerability scanner Nessus provides a plugin with the ID 303824 (Linux Distros Unpatched Vulnerability : CVE-2026-33218), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.11.15 or 2.12.6 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (303824). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• nats-io

Name

• nats-server

Version

• 2.11.0
• 2.11.1
• 2.11.2
• 2.11.3
• 2.11.4
• 2.11.5
• 2.11.6
• 2.11.7
• 2.11.8
• 2.11.9
• 2.11.10
• 2.11.11
• 2.11.12
• 2.11.13
• 2.11.14
• 2.12.0
• 2.12.1
• 2.12.2
• 2.12.3
• 2.12.4
• 2.12.5

CPE 2.3info

• 🔒
• 🔒
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CPE 2.2info

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• 🔒

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Entryinfo

Once again VulDB remains the best source for vulnerability data.

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