CVSS 3.1
4.2 mediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:NCVE-2026-33248
Medium (4.2) in linuxfoundation nats-server. EPSS 0.1% chance of exploitation in the next 30 days. Fixed in github.com/nats-io/nats-server/v2 2.11.15, 2.12.6.
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.
Severity
- EPSS
- 0.1% chance of exploitation in the next 30 days; higher than 4% of CVEs (scores of 2026-10-31)
- CWEs
- CWE-287, CWE-295
- Published
- Modified
- Record from
- the NVD, synced
Affected
- linuxfoundation:nats-server
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-3f24-pcvm-5jqc | Go | github.com/nats-io/nats-server/v2 | <2.11.15 | 2.11.15 |
| GHSA-3f24-pcvm-5jqc | Go | github.com/nats-io/nats-server/v2 | >=2.12.0-RC.1 <2.12.6 | 2.12.6 |
| GHSA-3f24-pcvm-5jqc | Go | github.com/nats-io/nats-server | all versions | no fix published |
| GO-2026-4828 | Go | github.com/nats-io/nats-server | all versions | no fix published |
| GO-2026-4828 | Go | github.com/nats-io/nats-server/v2 | <2.11.15 >=2.12.0-RC.1 <2.12.6 | 2.11.15, 2.12.6 |