CVE-2026-33248

low-risk

Published 2026-03-25

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.

Do I need to act?

0.02% chance of exploitation

EPSS score — low exploit probability

Not on CISA KEV list

No confirmed active exploitation reported to CISA

Patch status unknown

Check vendor advisories for fix availability and mitigation guidance

CVSS 4.2/10 Medium

NETWORK / HIGH complexity

Affected Products (1)

Nats-Server

Affected Vendors

Linuxfoundation

References (2)

Vendor Advisory https://advisories.nats.io/CVE/secnote-2026-13.txt

Vendor Advisory https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc

/ 100

low-risk

Severity 14/34 · Moderate

Exploitability 0/34 · Minimal

Exposure 5/34 · Minimal