CVE-2026-33219

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Source
https://cve.org/CVERecord?id=CVE-2026-33219
Import Source
https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-33219.json
JSON Data
https://api.test.osv.dev/v1/vulns/CVE-2026-33219
Aliases
Downstream
Related
Published
2026-03-25T19:55:28.363Z
Modified
2026-05-28T03:54:33.730198225Z
Severity
  • 5.3 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L CVSS Calculator
Summary
NATS is vulnerable to pre-auth DoS through WebSockets client service
Details

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.

Database specific 
{
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33219.json",
    "cwe_ids": [
        "CWE-770"
    ],
    "cna_assigner": "GitHub_M"
}
References

Affected packages

Git / github.com/nats-io/nats-server

Affected ranges

Type
GIT
Repo
https://github.com/nats-io/nats-server
Events
Introduced
4dccf778573cd9a9e52fb8f119718459f6f2f761
Fixed
0e0639058e0d2d8fce0cc34941f9897da152ab32

Affected versions

v2.*
v2.12.0
v2.12.0-RC.1
v2.12.0-RC.2
v2.12.0-RC.3
v2.12.0-RC.4
v2.12.0-RC.5
v2.12.0-RC.6
v2.12.1
v2.12.1-RC.1
v2.12.1-RC.2
v2.12.1-RC.3
v2.12.1-RC.4
v2.12.1-RC.5
v2.12.2
v2.12.2-RC.1
v2.12.2-RC.2
v2.12.2-RC.3
v2.12.2-RC.4
v2.12.3
v2.12.3-RC.1
v2.12.3-RC.2
v2.12.3-RC.3
v2.12.3-RC.4
v2.12.3-RC.5
v2.12.4
v2.12.4-RC.1
v2.12.4-RC.2
v2.12.4-RC.3
v2.12.4-RC.4
v2.12.4-RC.5
v2.12.4-RC.6
v2.12.5
v2.12.5-RC.1
v2.12.5-RC.2

Database specific

source 
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-33219.json"