What’s Vulnerable › Vulnerabilities

CVE-2026-58250: NATS Server: Pre-auth server crash via double INFO in leafnode handshake

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-08 · updated 2026-10-25
• Weakness: CWE-476

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.

Affected products

• nats-io nats-server: before 2.11.17; from 2.12.0 before 2.12.8 — fixed in 2.11.17, 2.12.8

How to fix

Upgrade to a fixed version: nats-io nats-server 2.11.17, 2.12.8. Check the vendor advisory for mitigations.

References

• 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/releases/tag/v2.11.17
• https://github.com/nats-io/nats-server/releases/tag/v2.12.8
• https://github.com/nats-io/nats-server/security/advisories/GHSA-3g5q-cfh2-cq67

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