5.3

CVE-2026-33219: linuxfoundation nats-server

CVSS: 5.3v3.1MediumModified
AliasesUBUNTU-CVE-2026-33219DEBIAN-CVE-2026-33219CGA-63w2-rrqv-9w2r
Published 25-03-2026Last modified 09-09-2026
Open JSON

Vulnerability summary

CVE-2026-33219 is a medium (CVSS 5.3) vulnerability in linuxfoundation nats-server. EPSS estimates a 1.00% chance of exploitation in the next 30 days, higher than 62.2% of scored vulnerabilities.

Overall risk
21/100
0100
Low · default modelHow is this calculated?
CVSS score
5.3/10
010
Medium · v3.1 (CVE.org)
EPSS score
1.00%
0%100%
Low · +0.47 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2 · Related 4
OPENSUSE-SU-2026:21483-1SUSE-SU-2026:1135-1CGA-JMWC-C8GG-J9HPCVE-2026-27571

Timeline

  1. 25-03-2026
    PublishedVulnerability first disclosed.
  2. 09-09-2026
    Last modifiedVulnerability information updated.

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 metrics

7 scores · 7 sources · 1 version

EPSS trend

Probability

1.00%

Chance of exploitation in the next 30 days

Percentile

62%

Versus all other CVEs

30-day change

+0.47 pp

From 0.53% on 19-09-2026

19-09-202619-10-2026
EPSS score
1.00%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard28 products
  • k3s< 1.35.2.1-r4
  • k3s-1.32< 1.32.13.1-r7
  • k3s-1.33< 1.33.9.1-r6
  • k3s-static< 1.35.2.1-r4
  • k3s-static-1.32< 1.32.13.1-r7
Wolfi12 products
  • k3s< 1.35.2.1-r4
  • k3s-1.32< 1.32.13.1-r7
  • k3s-1.33< 1.33.9.1-r6
  • k3s-static< 1.35.2.1-r4
  • k3s-static-1.32< 1.32.13.1-r7
Debian1 product
  • nats-serverAll versions (No fix recorded) | < 2.12.6-1
Github.com/nats-io1 product
  • nats-serverAll versions (No fix recorded)
Github.com/nats-io/nats-server1 product
  • v2< 2.11.15 | ≥ 2.12.0-RC.1, < 2.12.6
Linuxfoundation1 product
Nats-io1 product
Ubuntu1 product
  • nats-serverAll versions (No fix recorded)

8 vendors · 46 products

References

16 links
Show all 16 references