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CVE-2026-33248

NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching

Published: Mar 25, 2026Updated: Mar 26, 2026 Sources: CVE List NVDCWE-287
NVD MITRE
4.2CVSSMEDIUM
EPSS Score
0.1%
Top 96.1%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

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.

CVSS Vector Breakdown

AV:NAC:HPR:LUI:NS:UC:LI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:LConfidentiality
Low
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-287CWE-295

Affected Products

nats-servernats-io
On-prem
Databases / cache-message-queue
nats-serverlinuxfoundation
Mixed
AI / ML / ml-framework
nats-iooss-projectDatabases
linuxfoundationoss-projectUSAI / MLaka yocto, pytorch, everest

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available

MITRE ATT&CK

3 techniques
Collection
Initial Access
View detailed technique mapping

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc
github.com
https://advisories.nats.io/CVE/secnote-2026-13.txt
advisories.nats.io

Timeline

Published
Mar 25, 2026
Last Updated
Mar 26, 2026

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