Improper Handling of Unexpected Data Type Affecting github.com/nats-io/nats-server/v2/server package, versions <2.11.15>=2.12.0-RC.1 <2.12.6
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published25 Mar 2026
- disclosed24 Mar 2026
- creditUnknown
Introduced: 24 Mar 2026
CVE-2026-33218 Â (opens in a new tab)How to fix?
Upgrade github.com/nats-io/nats-server/v2/server to version 2.11.15, 2.12.6 or higher.
Overview
github.com/nats-io/nats-server/v2/server is an A simple, secure and performant communications system for digital systems, services and devices.
Affected versions of this package are vulnerable to Improper Handling of Unexpected Data Type through the leafnode connection handling in setLeafConnectDelayIfSoliciting in the **server/leafnode.go component. An attacker can crash the server by sending a malformed pre-authentication leafnode message, such as a loop-detected -ERR before CONNECT.
Workaround
This vulnerability can be mitigated by disabling leafnode support if not needed or by restricting network connections to the leafnode port.