CVE-2026-33215 NATS is vulnerable to MQTT hijacking via Client ID
Attackers can hijack MQTT sessions and messages by manipulating Client IDs, allowing unauthorized access to data and sessions in NATS-Server.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33215?
CVE-2026-33215 is a medium-severity authentication bypass vulnerability in nats-io nats-server, published on 24 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server provides an MQTT client interface. Prior to versions 2.11.15 and 2.12.5, Sessions and Messages can by hijacked via MQTT Client ID malfeasance. Versions 2.11.15 and 2.12.5 patch the issue. No known workarounds are available.
Which versions are affected by CVE-2026-33215?
7 open source packages ship an affected version, including github.com/nats-io/nats-server/v2, nats and github.com/nats-io/nats-server. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/nats-io/nats-server/v2 Go | All versions | 2.11.15, 2.12.6 |
github.com/nats-io/nats-server/v2 Go | All versions | 2.11.15 |
github.com/nats-io/nats-server/v2 Go | All versions | 2.11.15 |
github.com/nats-io/nats-server/v2 Go | From 2.12.0-RC.1 | 2.12.6 |
github.com/nats-io/nats-server/v2 Go | From 2.12.0-RC.1 | 2.12.6 |
nats Bitnami | All versions | 2.11.15, 2.12.6 |
1 more packages
github.com/nats-io/nats-server Go | All versions | None |
Products include Linuxfoundation Nats-Server.
How do I fix CVE-2026-33215?
Upgrade github.com/nats-io/nats-server/v2 to a fixed version for your release line: 2.11.15 or 2.12.6.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-33215 being exploited?
There is no known exploitation of CVE-2026-33215 in the wild and no public exploit code.
Other vulnerabilities in nats-io nats-server
- CVE-2022-28357 NATS nats-server allows directory traversal via unintended path to a management action
- CVE-2026-58253 NATS Server: Route API Auth Bypass
- CVE-2022-24450 Incorrect Authorization in NATS nats-server
- CVE-2026-33216 NATS has MQTT plaintext password disclosure
- CVE-2026-58207 NATS Server: Remote crash via integer overflow in Connz pagination
Sources
Also known as BIT-nats-2026-33215, CLEANSTART-2026-WK59830, DEBIAN-CVE-2026-33215, ECHO-8fee-c8db-8f5d, GHSA-fcjp-h8cc-6879, GO-2026-4833 and 10 more.