NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching
Summary
NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching
Original description
The description as published by the source.
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.
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-33248 nats-server
- Ubuntu UBUNTU-CVE-2026-33248 nats-server
References
- advisory advisories.nats.io
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com