Vulnerability Report

CVE-2026-33248

Title: mTLS Authentication Bypass in NATS-Server

Auth Bypass

Proof Of Concept

No public PoC currently indexed for CVE-2026-33248.

CWE Category CWE-287

Published Date Mar 25, 2026

Modified Date Mar 26, 2026

Exploit Status Not Found

Score 4.2 CVSS v3.1

Exploit Probability (EPSS)

0.01%

Vulnerability Summary

CVE-2026-33248: 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 consider highly unlikely. So this is an unlikely attack. Nonetheless, administrators who have been very sophisticated in their `DN` construction patterns might conceivably be impacted. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, developers should review their CA issuing practices.

Impacted Vendors

linuxfoundation 1

Reference Links

https://advisories.nats.io/CVE/secnote-2026-13.txt https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc

CVSS v3.1

Source Entity [email protected]

Severity MEDIUM

4.2

Attack Vector

NETWORK

Complexity

HIGH

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

RAW VECTOR CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2026-33248 Exploits & PoCs (Proof Of Concept)

No public PoCs found in our database for this CVE.

March 26, 2026 MODIFIED

Vulnerability data updated via NVD.

March 26, 2026 MODIFIED

Vulnerability data updated via NVD.

March 26, 2026 MODIFIED

Vulnerability data updated via NVD.

March 25, 2026 MODIFIED

Vulnerability data updated via NVD.

Attack Vector Matrix

Access Vector NETWORK

Complexity HIGH

Privileges N/A

Interaction NONE

CVSS Vector String


                                    CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N

Affected Stack

No specific products linked.