WebSocket Vulnerability in NATS-Server by NATS.io
CVE-2026-27889

7.5HIGH

Key Information:

Vendor

Nats-io

Status
Nats-server
Vendor
CVE Published:
25 March 2026

What is CVE-2026-27889?

The NATS-Server, a high-performance messaging server for NATS.io, has a vulnerability that arises from an absent sanity check on WebSocket frames. This flaw can lead to a server panic and is exploitable by any user who can connect to an exposed WebSockets port, as it occurs prior to authentication. The issue primarily affects versions 2.2.0 through 2.11.13 and 2.12.0 through 2.12.4. Users of NATS-Server should upgrade to versions 2.11.14 or 2.12.5 to mitigate this vulnerability. It is recommended to implement network access restrictions and utilize the available workaround to enhance security against potential attacks.

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Deploy the Patch

Affected Version(s)

nats-server >= 2.2.0, < 2.11.14 < 2.2.0, 2.11.14

nats-server >= 2.12.0, < 2.12.5 < 2.12.0, 2.12.5

References

https://github.com/nats-io/nats-server/security/advisorie...
x_refsource_CONFIRM
https://advisories.nats.io/CVE/secnote-2026-03.txt
x_refsource_MISC

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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