CVE-2026-14198
Auth bypass via encoded slash in parameter paths; @fastify/middie 9.1.0-9.3.2; patch 9.3.3.
Is CVE-2026-14198 being exploited?
Not confirmed. CVE-2026-14198 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 0.52% probability of exploitation in the next 30 days.
How severe is CVE-2026-14198?
CVE-2026-14198 is rated Critical with a CVSS score of 9.1. 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-2026-14198?
Yes. A fix has been recorded for CVE-2026-14198. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-14198 affect?
CVE-2026-14198 affects @fastify/middie 9.1.0-9.3.2. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-14198?
Upgrade to 9.3.3; avoid param middleware path decisions or add post-router auth.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker can bypass authentication and reach protected handlers by sending a crafted URL with %2F in a parameter.
Immediate action required
- affected>= 9.1.0 and < 9.3.3
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.