Memory Vulnerability in NATS-Server by NATS.io
CVE-2026-33219

5.3MEDIUM

Key Information:

Vendor

Nats-io

Status
Nats-server
Vendor
CVE Published:
25 March 2026

What is CVE-2026-33219?

A vulnerability in NATS-Server lets a malicious client connect to the WebSockets port and cause excessive memory usage before authentication. This requires the client to send a substantial amount of data, which can potentially hinder server performance. Versions 2.11.15 and 2.12.6 include fixes for this issue. Users are advised to disable WebSockets if they are not essential for deployment.

Affected Version(s)

nats-server < 2.11.15 < 2.11.15

nats-server >= 2.12.0-RC.1, < 2.12.6 < 2.12.0-RC.1, 2.12.6

References

https://github.com/nats-io/nats-server/security/advisorie...
x_refsource_CONFIRM
https://advisories.nats.io/CVE/secnote-2026-02.txt
x_refsource_MISC
https://advisories.nats.io/CVE/secnote-2026-11.txt
x_refsource_MISC

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
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

.