NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.
One authentication model supported is mTLS, deriving the NATS client identity from properties of the TLS Client Certificate.
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.
Fixed in nats-server 2.12.6 & 2.11.15
Developers should review their CA issuing practices.
| Score | Percentile |
|---|---|
| 0.02% | 4.59% |
| Base score | Version | Severity | Vector |
|---|---|---|---|
| 4.2 | 3.1 | — |
|
| Type | Value |
|---|---|
| GHSA | GHSA-3f24-pcvm-5jqc ↗ |
| CVE | CVE-2026-33248 ↗ |
Vulnerable version ranges and first patched releases as published by GitHub.
| Ecosystem | Package | Vulnerable range | First patched | Vulnerable functions |
|---|---|---|---|---|
| go | github.com/nats-io/nats-server/v2 | < 2.11.15 | 2.11.15 | — |
| go | github.com/nats-io/nats-server/v2 | >= 2.12.0-RC.1, < 2.12.6 | 2.12.6 | — |
| go | github.com/nats-io/nats-server | > 0 | — | — |