CVE-2026-33248

unknown

Published 2026-03-24 · Modified 2026-03-27

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CVSS v3

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

CVSS v4 NEW

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not yet in upstream

VIR risk

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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.

Predictions

Exploit likelihood

30%

Patch ETA

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Heuristic predictions, AS-IS, for prioritization only.

Mitigations

Mitigation details

Source: Debian Security Tracker · View original ↗ · DFSG

CVE-2026-33248 NameCVE-2026-33248 DescriptionNATS-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.…

Workaround

, developers should review their CA issuing practices. SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more) Vulnerable and fixed packages The table below lists information on source packages. Source PackageReleaseVersionStatus nats-server (PTS)bookworm2.9.10-1vulnerable trixie2.10.27-1vulnerable forky, sid2.14.1-1fixed The information below is based on the following data on fixed versions. PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs nats-serversource(unstable)2.12.6-1 Notes https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc https://advisories.nats.io/CVE/secnote-2026-13.txt

CVE-2026-33248

Name	CVE-2026-33248
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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
nats-server (PTS)	bookworm	2.9.10-1	vulnerable
	trixie	2.10.27-1	vulnerable
	forky, sid	2.14.1-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
nats-server	source	(unstable)	2.12.6-1

Notes

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

Home - Debian Security - Source (Git)

Apply commands

text fix

Notes

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

OS impact

OS	Version	Status	Fixed in
sles		affected
debian	bookworm	affected
debian	forky	fixed	`2.12.6-1`
debian	sid	fixed	`2.12.6-1`
debian	trixie	affected

Package impact

Ecosystem	Package	Vulnerable	Fixed
Go	github.com/nats-io/nats-server/v2	`<2.11.15`	`2.11.15`
Go	github.com/nats-io/nats-server/v2	`>=2.12.0-RC.1,<2.12.6`	`2.12.6`
Go	github.com/nats-io/nats-server

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.