CVE-2026-33223: NATS Server: Incomplete Stripping of Nats-Request-Info Header Allows Identity Spoofing
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 offers a Nats-Request-Info: message header, providing information about a request.
Problem Description
The NATS message header Nats-Request-Info: is supposed to be a guarantee of identity by the NATS server, but the stripping of this header from inbound messages was not fully effective.
An attacker with valid credentials for any regular client interface could thus spoof their identity to services which rely upon this header.
Affected Versions
Any version before v2.12.6 or v2.11.15
Workarounds
None.
Other sources
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, the NATS message header Nats-Request-Info: is supposed to be a guarantee of identity by the NATS server, but the stripping of this header from inbound messages was not fully effective. An attacker with valid credentials for any regular client interface could thus spoof their identity to services which rely upon this header. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-33223?
CVE-2026-33223 is classified as a high severity vulnerability in NATS.io.
How do I fix CVE-2026-33223?
To mitigate CVE-2026-33223, upgrade the NATS server to version 2.12.6 or later, or to version 2.11.15 if using an earlier version.
What versions are affected by CVE-2026-33223?
CVE-2026-33223 affects NATS server versions from 2.12.0-RC.1 to 2.12.6 and all versions prior to 2.11.15.
What does CVE-2026-33223 affect?
CVE-2026-33223 affects the request information handling in the NATS server communications.
Is there a known exploit for CVE-2026-33223?
As of now, there are no public exploits specifically targeting CVE-2026-33223 reported in the wild.