Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Linuxfoundation | Nats-Server | < 2.11.15 |
Related Weaknesses (CWE)
References
- https://advisories.nats.io/CVE/secnote-2026-13.txtVendor Advisory
- https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqcVendor Advisory
FAQ
What is CVE-2026-33248?
CVE-2026-33248 is a vulnerability with a CVSS score of 4.2 (MEDIUM). 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 deri...
How severe is CVE-2026-33248?
CVE-2026-33248 has been rated MEDIUM with a CVSS base score of 4.2/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-33248?
Check the references section above for vendor advisories and patch information. Affected products include: Linuxfoundation Nats-Server.