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Review reviewHigh

CVE-2026-27889

nats-io nats-server, Multicluster Global Hub 1.5.4, Red Hat multicluster global hub 1.4.4

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in dep...

CVSS
7.5
EPSS
0.58%
44.5% percentile
CISA KEV
Not listed
Published
2026.03.26
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.58%
Technical severityCVSS 7.5

Vulnerability overview

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in dep...

Affected product and versions

Product
nats-io nats-server, Multicluster Global Hub 1.5.4, Red Hat multicluster global hub 1.4.4
Affected versions
>= >= 2.2.0, < 2.11.14, >= >= 2.12.0, < 2.12.5, >= 2.2.0 < 2.11.14, >= 2.12.0 < 2.12.5
Fixed versions
2.11.14, 2.12.5

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that nats-io nats-server, Multicluster Global Hub 1.5.4, Red Hat multicluster global hub 1.4.4 and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
CWE-1286, CWE-190