CVE-2026-33248 Details
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 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.
An authentication bypass vulnerability has been identified in NATS-Server versions prior to 2.11.15 and 2.12.6. When using mutual TLS (mTLS) for client identity, certain patterns of Relative Distinguished Name (RDN) in the client certificate's Subject Distinguished Name (DN) were not properly enforced. This flaw allowed for authentication bypass, although it is considered an unlikely attack scenario. The vulnerability requires a valid certificate from a Certificate Authority (CA) trusted for client certificates, and specific DN naming patterns that are rarely used. However, administrators with complex DN constructions could be affected.
Users can upgrade to NATS-Server versions 2.12.6 or 2.11.15, both of which include the necessary fix. Additionally, it is recommended to review CA issuing practices to ensure that DN patterns do not inadvertently create vulnerabilities.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Mar 26, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://advisories.nats.io/CVE/secnote-2026-13.txt | [email protected] | Vendor Advisory |
| https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-287 | Improper Authentication | [email protected] |
| CWE-295 | Improper Certificate Validation | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| linuxfoundation nats-server | < 2.11.15 >= 2.12.0, < 2.12.6 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Mar 26, 2026 | Initial Analysis | [email protected] |
| Mar 25, 2026 | New CVE Received | [email protected] |