nats-io nats-server up to 2.11.14/2.12.5 Nats-Request-Info Identity Header authentication spoofing

Summaryinfo

A vulnerability marked as critical has been reported in nats-io nats-server up to 2.11.14/2.12.5. This vulnerability affects unknown code of the component Nats-Request-Info Identity Header Handler. This manipulation causes authentication spoofing. This vulnerability appears as CVE-2026-33246. The attack may be initiated remotely. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability has been found in nats-io nats-server up to 2.11.14/2.12.5 and classified as critical. Affected by this vulnerability is an unknown code of the component Nats-Request-Info Identity Header Handler. The manipulation with an unknown input leads to a authentication spoofing vulnerability. The CWE definition for the vulnerability is CWE-290. This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server offers a `Nats-Request-Info:` message header, providing information about a request. This is supposed to provide enough information to allow for account/user identification, such that NATS clients could make their own decisions on how to trust a message, provided that they trust the nats-server as a broker. A leafnode connecting to a nats-server is not fully trusted unless the system account is bridged too. Thus identity claims should not have propagated unchecked. Prior to versions 2.11.15 and 2.12.6, NATS clients relying upon the Nats-Request-Info: header could be spoofed. This does not directly affect the nats-server itself, but the CVSS Confidentiality and Integrity scores are based upon what a hypothetical client might choose to do with this NATS header. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-33246. The exploitation appears to be easy. The attack can be launched remotely. Neither technical details nor an exploit are publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 303842 (Linux Distros Unpatched Vulnerability : CVE-2026-33246), 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 (303842). Several companies clearly confirm that VulDB is the primary source for best 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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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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