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Vulnerability record · CVE-2026-33219 · published 25 March 2026

CVE-2026-33219: Linuxfoundation nats-server allocation without limits vulnerability

Linuxfoundation · Nats Server

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.

5.3 CVSS 3.1 Medium EPSS 1.0% · top 38.6% CWE-770 · Allocation without limits
5.3CVSS 3.1 base score
1.0%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
10References
9 Sep 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://advisories.nats.io/CVE/secnote-2026-02.txt MitigationVendor Advisory
https://advisories.nats.io/CVE/secnote-2026-11.txt MitigationVendor Advisory
https://github.com/advisories/GHSA-qrvq-68c2-7grw MitigationVendor Advisory
https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j MitigationVendor Advisory
https://access.redhat.com/errata/RHSA-2026:21769
https://access.redhat.com/errata/RHSA-2026:22347
https://access.redhat.com/errata/RHSA-2026:23345
https://access.redhat.com/security/cve/CVE-2026-33219
https://bugzilla.redhat.com/show_bug.cgi?id=2451445
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33219.json

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2022-28357Linuxfoundation nats-server path traversal vulnerabilityNATS nats-server 2.2.0 through 2.7.4 allows directory traversal because of an unintended path to a management action from a management account.EPSS 1.2%9.8CVE-2020-26892Linuxfoundation nats-server hard-coded credentials vulnerabilityThe JWT library in NATS nats-server before 2.1.9 has Incorrect Access Control because of how expired credentials are handled.EPSS 2.1%8.8CVE-2026-58253Linuxfoundation nats-server improper authentication vulnerabilityNATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.0, 2.12.7, and 2.11.16, when no_auth_…EPSS 0.37%8.8CVE-2022-24450Linuxfoundation nats-server missing authorization vulnerabilityNATS nats-server before 2.7.2 has Incorrect Access Control. Any authenticated user can obtain the privileges of the System account by misusing the "d…EPSS 1.3%7.5CVE-2026-58208Linuxfoundation nats-server vulnerabilityNATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, a WebSocket listener c…EPSS 0.60%7.5CVE-2026-58250Linuxfoundation nats-server null pointer dereference vulnerabilityNATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.12.8 and 2.11.17, an unauthenticated pee…EPSS 0.74%7.5CVE-2026-58210Linuxfoundation nats-server uncontrolled resource consumption vulnerabilityNATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, an unauthenticated MQT…EPSS 0.74%7.5CVE-2026-33216Linuxfoundation nats-server vulnerabilityNATS-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, for MQTT deploy…EPSS 0.63%

Source: NIST National Vulnerability Database (record CVE-2026-33219), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.