CVE-2026-33248: NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching

CVE-2026-33248 · Severity: low · CVSS 3.1 · Published 2026-03-26

NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching in github.com/nats-io/nats-server

Technologies: github.com/nats-io/nats-server (Go), github.com/nats-io/nats-server/v2 (Go). Vendors: Go.

Quick answers

Is CVE-2026-33248 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-33248 being exploited in the wild.
How severe is CVE-2026-33248?
Low severity, with a CVSS score of 3.1, published 26 March 2026.
Which products and versions are affected?
github.com/nats-io/nats-server (Go) SEMVER:introduced=0; github.com/nats-io/nats-server/v2 (Go) SEMVER:introduced=0,fixed=2.11.15, SEMVER:introduced=0,fixed=2.11.15,introduced=2.12.0-RC.1,fixed=2.12.6.
Is there a fix for CVE-2026-33248?
Yes. github.com/nats-io/nats-server/v2 (Go): upgrade to 2.11.15, 2.12.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-33248?
Check whether you run github.com/nats-io/nats-server (Go) or github.com/nats-io/nats-server/v2 (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/nats-io/nats-server/v2 (Go): upgrade to 2.11.15, 2.12.6 or later
    go get github.com/nats-io/nats-server/v2@v2.12.6

Affected products

  • github.com/nats-io/nats-server (Go) SEMVER:introduced=0
  • github.com/nats-io/nats-server/v2 (Go) SEMVER:introduced=0,fixed=2.11.15, SEMVER:introduced=0,fixed=2.11.15,introduced=2.12.0-RC.1,fixed=2.12.6

Identifiers

  • CVE-2026-33248
  • GHSA-3f24-pcvm-5jqc
  • GO-2026-4828

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