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Fencer Vulns
medium 6.4

CVE-2026-33246 json

NATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers

published 2026-03-24 7 mo ago modified 2026-09-10 1 mo ago also BIT-nats-2026-33246 , EUVD-2026-15973 , GHSA-55h8-8g96-x4hj , GO-2026-4830 , JLSEC-2026-1130

cvss
6.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 4%
public exploits
0
none known

Summary

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server offers a `Nats-Request-Info:` message header, providing information about a request. This is supposed to provide enough information to allow for account/user identification, such that NATS clients could make their own decisions on how to trust a message, provided that they trust the nats-server as a broker. A leafnode connecting to a nats-server is not fully trusted unless the system account is bridged too. Thus identity claims should not have propagated unchecked. Prior to versions 2.11.15 and 2.12.6, NATS clients relying upon the Nats-Request-Info: header could be spoofed. This does not directly affect the nats-server itself, but the CVSS Confidentiality and Integrity scores are based upon what a hypothetical client might choose to do with this NATS header. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.

Patch / fix

  • go github.com/nats-io/nats-server/v2 2.11.15, 2.12.6
  • bitnami nats 2.11.15, 2.12.6
  • julia nats_server_jll 2.14.3+0
  • linuxfoundation nats-server 2.11.15, 2.12.6
  • nats nats_server 2.11.15, 2.12.6
  • nats nats_streaming_server 2.11.15, 2.12.6
  • nats-server Debian 14 2.12.6-1

debian advisories DEBIAN-CVE-2026-33246

  • govulncheck-vulndb openSUSE Leap 15.6 0.0.20260326T203309-150000.1.155.2

suse advisories SUSE-SU-2026:1135-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

  • nats-server Alpine 3.24, Alpine 3.23 2.12.6-r0

alpine advisories ALPINE-CVE-2026-33246

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-33246 updated cvss 6.4

nats-server: nats: github.com/nats-io/nats-server: NATS-Server: Client identity spoofing via Nats-Request-Info header manipulation

  • Red Hat Multicluster Global Hub multicluster-globalhub/multicluster-globalhub-grafana-rhel9 Red Hat OpenShift Container Platform 4 openshift4/oc-mirror-plugin-rhel9
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
GitHub 3.1 6.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
NVD 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
OSV 3.1 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
go github.com/nats-io/nats-server/v2
<2.11.15
>=2.12.0-RC.1, <2.12.6
2.11.15
2.12.6
go github.com/nats-io/nats-server
all versions
 no fix listed
bitnami nats
<2.11.15
>=2.12.0, <2.12.6
2.11.15
2.12.6
julia nats_server_jll
<2.14.3+0
2.14.3+0

Affected products

  • nats-io nats-server

Classification

Weakness
  • CWE-287 Improper Authentication
  • CWE-290 Authentication Bypass by Spoofing

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.