CVE-2026-33248 — Improper Authentication in Nats-server

CWE-287 — Improper AuthenticationCWE-295 — Improper Certificate ValidationCWE-289 — Authentication Bypass by Alternate Name8 documents6 sources
Severity
4.2MEDIUMNVD
EPSS
0.0%
top 93.52%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
4
Nats-io Nats-serverLinuxfoundation Nats-serverGithub.com Nats-io Nats-server V2+1 more
Timeline
PublishedMar 25
Latest updateMar 26

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, when using mTLS for client identity, with `verify_and_map` to derive a NATS identity from the client certificate's Subject DN, certain patterns of RDN would not be correctly enforced, allowing for authentication bypass. This does require a valid certificate from a CA already trusted for client certificates, and `DN` naming patterns which the NATS maintainers consi…

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:NExploitability: 1.6 | Impact: 2.5

Affected Packages5 packages

▶debiandebian/nats-server< nats-server 2.12.6-1 (forky)
▶CVEListV5nats-io/nats-server< 2.11.15+1
▶NVDlinuxfoundation/nats-server2.12.0 — 2.12.6+1
▶Gogithub.com/nats-io_nats-server_v22.12.0-RC.1 — 2.12.6+1
▶Debianlinuxfoundation/nats-server< 2.12.6-1

🔴Vulnerability Details

4
OSV
NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching in github.com/nats-io/nats-server↗2026-03-26
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OSV
CVE-2026-33248: NATS-Server is a High-Performance server for NATS↗2026-03-25
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OSV
NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching↗2026-03-24
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GHSA
NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching↗2026-03-24
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📋Vendor Advisories

2
Red Hat
github.com/nats-io/nats-server: nats: NATS-Server: Authentication bypass due to incorrect Subject DN matching during mTLS client identity verification↗2026-03-25
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Debian
CVE-2026-33248: nats-server - NATS-Server is a High-Performance server for NATS.io, a cloud and edge native me...↗2026
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🕵️Threat Intelligence

1
Wiz
CVE-2026-33248 Impact, Exploitability, and Mitigation Steps | Wiz↗
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