CVE-2026-33248Network attack vector

Authentication bypass via incorrect Subject DN matching

Published Mar 25, 2026 · Updated Mar 25, 2026

Authentication bypass in NATS Server before 2.11.15 and 2.12.0-RC.1 through 2.12.5 allows remote authenticated users to assume another identity. The verify_and_map path compares a certificate's parsed Subject DN with configured identities but incorrectly treats certain nonmatching RDN patterns as equivalent. The gate is a valid certificate from a trusted client CA plus an affected DN pattern; success grants the permissions assigned to the wrongly matched identity.

CVSS severity4.2
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in NATS Server before 2.11.15 and 2.12.0-RC.1 through 2.12.5 allows remote authenticated users to assume another identity. The verify_and_map path compares a certificate's parsed Subject DN with configured identities but incorrectly treats certain nonmatching RDN patterns as equivalent. The gate is a valid certificate from a trusted client CA plus an affected DN pattern; success grants the permissions assigned to the wrongly matched identity.

The record

CVE
CVE-2026-33248
Published
Mar 25, 2026
Updated
Mar 25, 2026
Vendor
NATS.io
Product
NATS Server
Classifications
CWE-295, CWE-287, T1078
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.11.15
  2. Affected versionversion=>= 2.12.0-RC.1, < 2.12.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

NATS.io · NATS Serverversion=< 2.11.15; version=>= 2.12.0-RC.1, < 2.12.6

Published CVSS scores

4.2GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
CWE-287Improper Authentication
T1078Valid Accounts

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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