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Fencer Vulns
high 7.5

CVE-2026-33219 json

NATS is vulnerable to pre-auth DoS through WebSockets client service

published 2026-03-24 7 mo ago modified 2026-09-10 59 d ago also BIT-nats-2026-33219 , EUVD-2026-15970 , GHSA-8r68-gvr4-jh7j , GO-2026-4831 , JLSEC-2026-1127

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/nats-io/nats-server/v2 2.11.15, 2.12.6
  • bitnami nats 2.11.15, 2.12.6
  • julia nats_server_jll 2.14.3+0
  • Red Hat Multicluster Global Hub 1.4.5 1779579439
  • Red Hat Multicluster Global Hub 1.6.5 1780167118
  • Red Hat Red Hat multicluster global hub 1.5.3 1778867753
  • nats-server Debian 14 2.12.6-1

debian advisories DEBIAN-CVE-2026-33219

  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20260326T203309-150000.1.155.2

suse advisories SUSE-SU-2026:1135-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

  • nats-server Alpine 3.24, Alpine 3.23 2.12.6-r0

alpine advisories ALPINE-CVE-2026-33219

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-33219 updated cvss 7.5

github.com/nats-io/nats-server: NATS-Server: Denial of Service via unbounded memory use in WebSockets

  • Red Hat Multicluster Global Hub 1.4.9 multicluster-globalhub/multicluster-globalhub-grafana-rhel9 1779579439
    fixed: vendor fix RHSA-2026:22347
  • Red Hat Multicluster Global Hub 1.6.5 multicluster-globalhub/multicluster-globalhub-grafana-rhel9 1780167118
    fixed: vendor fix RHSA-2026:23345
  • Red Hat multicluster global hub 1.5.3 multicluster-globalhub/multicluster-globalhub-grafana-rhel9 1778867753
    fixed: vendor fix RHSA-2026:21769
  • Red Hat Multicluster Global Hub 1.4.9 multicluster-globalhub/multicluster-globalhub-agent-rhel9 1779838819, multicluster-globalhub/multicluster-globalhub-manager-rhel9 1779839447, multicluster-globalhub/multicluster-globalhub-rhel9-operator 1779887217, multicluster-globalhub/multicluster-globalhub-operator-bundle 1779891163, multicluster-globalhub/multicluster-globalhub-postgres-exporter-rhel9 1779147132 Red Hat Multicluster Global Hub 1.6.5 multicluster-globalhub/multicluster-globalhub-agent-rhel9 1780320809, multicluster-globalhub/multicluster-globalhub-manager-rhel9 1780321673, multicluster-globalhub/multicluster-globalhub-rhel9-operator 1779839087, multicluster-globalhub/multicluster-globalhub-operator-bundle 1780370487, multicluster-globalhub/multicluster-globalhub-postgres-exporter-rhel9 1779839762 Red Hat multicluster global hub 1.5.3 multicluster-globalhub/multicluster-globalhub-agent-rhel9 1779828691, multicluster-globalhub/multicluster-globalhub-manager-rhel9 1779828813, multicluster-globalhub/multicluster-globalhub-rhel9-operator 1779828536, multicluster-globalhub/multicluster-globalhub-operator-bundle 1779837290, multicluster-globalhub/multicluster-globalhub-postgres-exporter-rhel9 1779835152 Red Hat OpenShift Container Platform 4 openshift4/oc-mirror-plugin-rhel9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
go github.com/nats-io/nats-server/v2
<2.11.15
>=2.12.0-RC.1, <2.12.6
2.11.15
2.12.6
go github.com/nats-io/nats-server
all versions
 no fix listed
bitnami nats
<2.11.15
>=2.12.0, <2.12.6
2.11.15
2.12.6
julia nats_server_jll
<2.14.3+0
2.14.3+0

Affected products

  • nats-io nats-server
  • Red Hat Multicluster Global Hub 1.4.5
  • Red Hat Multicluster Global Hub 1.6.5
  • Red Hat Red Hat multicluster global hub 1.5.3
  • Red Hat Red Hat OpenShift Container Platform 4

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.