CVE-2026-112712 @fastify/middie - Authentication Bypass

@fastify/middie 9.0.0 through 9.3.5 contains an authentication bypass caused by incorrect path joining in path-scoped middleware, letting attackers bypass middleware like authentication or rate limiting, exploit requires crafted request to mismatched path.

CVSS base score 9.1 /10
Critical
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Broken Authentication
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
20 October 2026
Updated
21 October 2026
Weakness
CWE-436

Vendor fix

Upgrade to version 9.3.6 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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