CVE-2026-58253
Auth bypass in NATS Server route/leafnode listeners allowing unauthenticated inter-server access
Is CVE-2026-58253 being exploited?
Not confirmed. CVE-2026-58253 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.37% probability of exploitation in the next 30 days.
How severe is CVE-2026-58253?
CVE-2026-58253 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-58253?
Yes. A fix has been recorded for CVE-2026-58253. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-58253 affect?
CVE-2026-58253 affects NATS Server < 2.14.0, < 2.12.7, < 2.11.16 when no_auth_user is configured. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-58253?
Upgrade to 2.14.0, 2.12.7, or 2.11.16; remove/limit no_auth_user and audit inter-server listeners
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthenticated peer can bypass inter-server CONNECT auth on route/leafnode listeners, impersonate servers, and publish/subscribe/read/modify messaging traffic.
Immediate action required
- affected< 2.11.16
- affected>= 2.12.0-preview.1 and < 2.12.6
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.