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TI-2026-58517 Aliases CVE-2026-85184

@fastify/middie vulnerable to path-scoped middleware bypass via absolute-form request target

Priority MEDIUM 48CWE-436Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
High · High · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

@fastify/middie versions >= 9.1.0 and before 9.3.4 decide whether to run path-scoped middleware by matching against the raw request target, while the Fastify router resolves an absolute-form request target to its path before dispatching. Because the two layers evaluate different strings, a request using an absolute-form target reaches the route handler while the path-scoped middleware, such as authentication or authorization, is skipped. An unauthenticated network attacker can use this to bypass path-based access controls in a Fastify application that relies on middie for those controls. Users should upgrade to @fastify/middie 9.3.4 or later.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00523 44th percentileScored 2026-11-07
Fix Fixed @fastify/middie (@fastify/middie): 9.3.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
fastify@fastify/middie9.1.0 to before 9.3.49.3.4Patch availableCNA
  • @fastify/middie Vendorfastify Affected 9.1.0 to before 9.3.4 Fixed in 9.3.4 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:fastify:fastify\/middie:*:*:*:*:*:node.js:*:*9.1.0 to before 9.3.4Vulnerablefastify
  • cpe:2.3:a:fastify:fastify\/middie:*:*:*:*:*:node.js:*:* Versions 9.1.0 to before 9.3.4 Vulnerable ·fastify

Remediation

  • Fix · CNA @fastify/middie (@fastify/middie) Fixed in 9.3.4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-85184

References

Advisory 2

  • TI-2026-05498 @fastify/middie vulnerable to middleware authentication bypass in child plugin scopes CVSS 3.1CRITICAL 9.1
  • TI-2026-17725 Fastify Middie Middleware Path Bypass CVSS 3.1HIGH 8.8
  • TI-2026-12029 @fastify/middie vulnerable to authorization bypass via encoded slash in path parameter values CVSS 3.1CRITICAL 9.1
  • TI-2026-26176 @fastify/middie vulnerable to middleware bypass via deprecated ignoreDuplicateSlashes option CVSS 3.1CRITICAL 9.1
  • TI-2026-12013 @fastify/middie standalone engine vulnerable to Denial of Service via malformed percent-encoded paths CVSS 3.1HIGH 7.5
  • TI-2026-02474 @fastify/middie has an improper path normalization vulnerability CVSS 4.0HIGH 8.2

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences