BIT-nats-2026-33248Published

NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching

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cve-program · CVE-2026-33248

Published

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 published: 25 Mar 2026 20:18:28 UTC
Source modified: 26 Mar 2026 19:52:12 UTC
Saved here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

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CVSS 3.1 · 4.2 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N

euvd · EUVD-2026-15999

Published

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EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

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datePublished: Mar 25, 2026, 8:18:28 PM

dateUpdated: Mar 26, 2026, 7:52:12 PM

1 related source bulletins · separate from aliases

WID-SEC-W-2026-0858: NATS Server: Mehrere Schwachstellen

CVE-2026-33215 · CVE-2026-33216 · CVE-2026-33217 · CVE-2026-33218 · CVE-2026-33219 · CVE-2026-33222 · CVE-2026-33223 · CVE-2026-33246 · CVE-2026-33247 · CVE-2026-33248 · CVE-2026-33249

Source published: Mar 25, 2026, 8:18:28 PM (timezone not stated)
Source modified: Mar 26, 2026, 7:52:12 PM (timezone not stated)
Saved here: 15 Nov 2026 20:52:54 UTC
Source terms: ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 4.2 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N

nvd · CVE-2026-33248

Published

Additional publisher context

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-287 · CWE-295

Original publisher date fields

published: 2026-03-25T21:16:47.563

lastModified: 2026-06-17T10:37:11.377

1 source CPE criteria · context only

cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Source published: 25 Mar 2026 21:16:47 UTC
Source modified: 17 Jun 2026 10:37:11 UTC
Saved here: 25 Oct 2026 08:17:18 UTC
Source terms: NIST NVD usage terms; underlying source attribution retained

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CVSS 3.1 · [email protected] · Secondary · 4.2 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N

osv · GHSA-3f24-pcvm-5jqc

Published

### Background 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. ### Problem Description 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. ### Affected Versions Fixed in nats-server 2.12.6 & 2.11.15 ### Workarounds Developers should review their CA issuing practices.

Source published: 24 Mar 2026 21:51:08 UTC
Source modified: 10 Sep 2026 03:50:36 UTC
Saved here: 24 Oct 2026 13:19:41 UTC
Source terms: GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N

Publisher rating · MODERATE

osv · GO-2026-4828

Published

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

Source published: 26 Mar 2026 20:33:02 UTC
Source modified: 27 Mar 2026 18:26:05 UTC
Saved here: 24 Oct 2026 13:19:41 UTC
Source terms: OSV · upstream source license applies

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