CVE-2026-58250: nats-server Null Dereference — Fix

Description

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.12.8 and 2.11.17, an unauthenticated peer with network access to a leafnode listener with compression enabled could crash the server during the pre-authentication leafnode handshake by sending repeated leafnode INFO protocol messages before authentication and account setup completed. This issue is fixed in versions 2.12.8 and 2.11.17.

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CVSS v3.1 Score

7.5

HIGH

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

EPSS — Exploit Prediction

0.0073

Probability of exploitation

0.51%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linuxfoundation	nats-server	< 2.11.17
linuxfoundation	nats-server	2.12.0 — 2.12.8

References

Advisories & Patches

https://github.com/nats-io/nats-server/commit/8dcb26eaea78fdcbe96dbee5986d6019fd5cb94a https://github.com/nats-io/nats-server/commit/fc5fe39177533e9dbdd651d2458285bfae1dde27 https://github.com/nats-io/nats-server/security/advisories/GHSA-3g5q-cfh2-cq67

Other References

https://github.com/nats-io/nats-server/releases/tag/v2.11.17 https://github.com/nats-io/nats-server/releases/tag/v2.12.8

Frequently Asked Questions

What is CVE-2026-58250? +

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.12.8 and 2.11.17, an unauthenticated peer with network access to a leafnode listener with compression enabled could crash the server during the pre-authentication leafnode handshake by sending repeated leafnode INFO protocol messages before authentication and account setup completed. This issue is fixed in versions 2.12.8 and 2.11.17. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-58250? +

CVE-2026-58250 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0073, placing it in the 1th percentile for exploitation probability.

What products are affected by CVE-2026-58250? +

CVE-2026-58250 affects products from linuxfoundation, specifically: nats-server. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-58250? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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