NATS is vulnerable to pre-auth DoS through WebSockets client service
Summary
| CVE | CVE-2026-33219 |
|---|---|
| State | PUBLISHED |
| Assigner | GitHub_M |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-03-25 20:16:32 UTC |
| Updated | 2026-06-30 03:18:38 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Problem Types: CWE-770 | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling | CWE-770 Allocation of Resources Without Limits or Throttling
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | ADP | CVSS | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | [email protected] | Secondary | 5.3 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| 3.1 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | Secondary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | DECLARED | 5.3 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Linuxfoundation | Nats-server | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Nats-io | Nats-server | affected < 2.11.15 | Not specified |
| CNA | Nats-io | Nats-server | affected >= 2.12.0-RC.1, < 2.12.6 | Not specified |
| ADP | Red Hat | Multicluster Global Hub 1.4.5 | Not specified | Not specified |
| ADP | Red Hat | Multicluster Global Hub 1.5.4 | Not specified | Not specified |
| ADP | Red Hat | Multicluster Global Hub 1.6.2 | Not specified | Not specified |
| ADP | Red Hat | Red Hat OpenShift Container Platform 4 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| advisories.nats.io/CVE/secnote-2026-02.txt | [email protected] | advisories.nats.io | Mitigation, Vendor Advisory |
| github.com/advisories/GHSA-qrvq-68c2-7grw | [email protected] | github.com | Mitigation, Vendor Advisory |
| security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33219.json | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | security.access.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-33219 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| bugzilla.redhat.com/show_bug.cgi | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | bugzilla.redhat.com | |
| access.redhat.com/errata/RHSA-2026:21769 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j | [email protected] | github.com | Mitigation, Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:23345 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:22347 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| advisories.nats.io/CVE/secnote-2026-11.txt | [email protected] | advisories.nats.io | Mitigation, Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| ADP | 2026-03-25T20:01:41.235Z | Reported to Red Hat. |
| ADP | 2026-03-25T19:55:28.363Z | Made public. |
Solutions
ADP: RHSA-2026:22347: Multicluster Global Hub 1.4.5
ADP: RHSA-2026:21769: Multicluster Global Hub 1.5.4
ADP: RHSA-2026:23345: Multicluster Global Hub 1.6.2
Workarounds
ADP: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
There are currently no legacy QID mappings associated with this CVE.