Vulnerability Report

CVE-2026-33219

Title: NATS-Server WebSockets Unbounded Memory Use

DoS

Proof Of Concept

No public PoC currently indexed for CVE-2026-33219.

CWE Category CWE-770

Published Date Mar 25, 2026

Modified Date Mar 26, 2026

Exploit Status Not Found

Score 5.3 CVSS v3.1

Exploit Probability (EPSS)

0.12%

Vulnerability Summary

CVE-2026-33219: NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, a malicious client which can connect to the WebSockets port can cause unbounded memory use in the nats-server before authentication; this requires sending a corresponding amount of data. This is a milder variant of CVE-2026-27571. That earlier issue was a compression bomb, this vulnerability is not. Attacks against this new issue thus require significant client bandwidth. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable websockets if not required for project deployment.

Impacted Vendors

linuxfoundation 1

Reference Links

https://advisories.nats.io/CVE/secnote-2026-02.txt https://advisories.nats.io/CVE/secnote-2026-11.txt https://github.com/advisories/GHSA-qrvq-68c2-7grw https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j

CVSS v3.1

Source Entity [email protected]

Severity MEDIUM

5.3

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2026-33219 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

March 26, 2026 MODIFIED

Vulnerability data updated via NVD.

March 26, 2026 MODIFIED

Vulnerability data updated via NVD.

March 26, 2026 MODIFIED

Vulnerability data updated via NVD.

March 25, 2026 MODIFIED

Vulnerability data updated via NVD.

Attack Vector Matrix

Access Vector NETWORK

Complexity LOW

Privileges N/A

Interaction NONE

CVSS Vector String


                                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected Stack

No specific products linked.