CVE-2026-33219

mediumpriority · track · 0EPSS 0.005 · 46 %ileDEEUUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
0.55% (46th) EPSS
CVSS 5.3 · medium
Is it mine?
14 products
Check your exposure
Who says so?
5 sources
cnnvd · enisa_euvd · osv · cert_bund

EPSS · scored 2026-10-27

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.

01

cvss

Technical severity, 0–10. One row per scoring source.

7.5
010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 5.3–7.5

v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Lsecondary · ENISA EU
v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Lsecondary · security-advisories@github.comexploitability 3.9 · impact 1.4
v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondaryexploitability 3.9 · impact 3.6
v3.15.3mediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Lsecondary · OSV
02

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Trackcoordinatorcisa_ssvcUS
03

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-770USCWE-770US
04

affected products (14)

Products and version ranges known to be affected.

05

advisories (4)

Vendor and ecosystem advisories describing this.

  • WID-SEC-W-2026-0858NATS Server: Mehrere SchwachstellenDeutsch2026-03-24csaf · cert_bundDE

    Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in NATS Server ausnutzen, um Informationen offenzulegen oder zu manipulieren, einen Denial-of-Service zu verursachen und Sicherheitsmechanismen zu umgehen.

  • GHSA-8r68-gvr4-jh7jNATS is vulnerable to pre-auth DoS through WebSockets client service2026-03-24ghsa · osvUS

    ### Background NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing. The nats-server offers a WebSockets client service, used in deployments where browsers are the NATS clients. ### Problem Description 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 [NATS-advisory-ID 2026-02](https://advisories.nats.io/CVE/secnote-2026-02.txt) (aka CVE-2026-27571; GHSA-qrvq-68c2-7grw). That earlier issue was a compression bomb, this vulnerability is not. Attacks against this new issue thus require significant client bandwidth. ### Affected Versions Any version before v2.12.6 or v2.11.15 ### Workarounds Disable websockets if not required for project deployment.

  • BIT-nats-2026-33219NATS is vulnerable to pre-auth DoS through WebSockets client service2026-03-27vendor · osvUS

    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.

  • GO-2026-4831NATS is vulnerable to pre-auth DoS through WebSockets client service in github.com/nats-io/nats-server2026-03-26vendor · osvUS

    NATS is vulnerable to pre-auth DoS through WebSockets client service in github.com/nats-io/nats-server

06

also known as (6)

Other names and identifiers for this entity.

07

sources

Which sources assert this record, and when.

cnnvdenisa_euvdosvcert_bundnvdNVDCVE.orgMITRE
published 2026-03-25modified 2026-09-09
08

references (20)

External citations — patches, advisories, analysis.

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