No exploitation reportedFix available

CVE-2026-33219

Q: Is CVE-2026-33219 actively exploited?

Active exploitation of CVE-2026-33219 has not been confirmed. Its EPSS score was 1.0% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2026-33219?

CVE-2026-33219 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

No exploitation reported by the sources we read.

Published2026-03-25
Fixed in2.12.6 · 2.11.15
WeaknessCWE-770

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC

2026-03-2520:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-33219?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-33219?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV

Linuxfoundation nats-server

Branch	Affected	Fixed in	Source
2.12	≥ 2.12.0, < 2.12.6	2.12.6	NVD · OSV
2.12	≥ 2.12.0-RC.1, < 2.12.6	2.12.6	OSV
2.11	< 2.11.15	2.11.15	NVD · OSV

nats-io/nats-server

Branch	Affected	Fixed in	Source
—	all versions	no fix published	OSV

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

RHSA-2026:23345 Red Hat Product Security4 products fixed
Red Hat Security Advisory: Multicluster Global Hub 1.6.2 security update
RHSA-2026:22347 Red Hat Product Security4 products fixed
Red Hat Security Advisory: Multicluster Global Hub 1.4.5 security update
RHSA-2026:21769 Red Hat Product Security4 products fixed
Red Hat Security Advisory: Multicluster Global Hub 1.5.4 security update

Full record on NVD

Fix

Update Linuxfoundation nats-server to 2.12.6 · 2.11.15
Vendor fix Red Hat Product Security RHSA-2026:23345 · 4 productsFor more details, see the Red Hat Advanced Cluster Management for Kubernetes documentation: https://docs.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.15/html/multicluster_global_hub/index
Vendor fix Red Hat Product Security RHSA-2026:22347 · 4 productsFor more details, see the Red Hat Advanced Cluster Management for Kubernetes documentation: https://docs.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.13/html/multicluster_global_hub/index
Vendor fix Red Hat Product Security RHSA-2026:21769 · 4 productsFor more details, see the Red Hat Advanced Cluster Management for Kubernetes documentation: https://docs.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.14/html/multicluster_global_hub/index
Workaround from the vendor Red Hat Product Security RHSA-2026:23345 · 21 productsMitigation 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.

Advisories and patches

advisories.nats.ioMitigation · Vendor Advisory
advisories.nats.ioMitigation · Vendor Advisory
github.comMitigation · Vendor Advisory
github.comMitigation · Vendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVE recordread 2026-10-23
CISA-ADPSSVC decisionnone2026-03-25
OpenCVESSVC decisionnone—
CNACVSS 3.15.3read 2026-10-23
CNAweakness (CWE)CWE-770read 2026-10-23
FIRST EPSSEPSS score1.0 %2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Published: 2026-03-25
Last Modified: 2026-09-09
NVD status: Modified

Frequently asked questions

What is CVE-2026-33219?

Is CVE-2026-33219 actively exploited?

Active exploitation of CVE-2026-33219 has not been confirmed. Its EPSS score was 1.0% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-33219?

CVE-2026-33219 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

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