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GHSA-3f24-pcvm-5jqc

MediumCVSS 4.2 / 10
Published Mar 24, 2026·Last modified Mar 27, 2026
Affected Components(0)

No affected components available

Description

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.

Risk Scores
Base Score
4.2

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
3.9

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.14%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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