How severe is CVE-2026-58211?

CVE-2026-58211 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2026-58211 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-58211?

CVE-2026-58211 affects Linuxfoundation Nats-server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-58211?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-58211 published?

CVE-2026-58211 was published on 2026-07-08 and last updated on 2026-07-09.

CVE-2026-58211

CVE-2026-58211 is a medium-severity vulnerability in Linuxfoundation Nats-server with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-863.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Linuxfoundation Nats-server
Published: 2026-07-08
Last modified: 2026-07-09

Description

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, a client could be registered as the configured no_auth_user through a parser path used when the first client operation was not CONNECT, bypassing user-level connection restrictions such as allowed_connection_types or proxy_required that normal authentication would apply. This issue is fixed in versions 2.14.3 and 2.12.12.

Frequently asked questions

What is CVE-2026-58211?: NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, a client could be registered as the configured no_auth_user through a parser path used when the first client operation was not CONNECT, bypassing user-level connection restrictions such as allowed_connection_types or proxy_required that normal authentication would apply. This issue is fixed in versions 2.14.3 and 2.12.12.
How severe is CVE-2026-58211?: CVE-2026-58211 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2026-58211 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-58211?: CVE-2026-58211 affects Linuxfoundation Nats-server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-58211?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-58211 published?: CVE-2026-58211 was published on 2026-07-08 and last updated on 2026-07-09.

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-hmmp-q8cx-v964

Affected products (1)

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

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