Unauthenticated access-control bypass via absolute-form targets
Published Sep 4, 2026 · Updated Sep 4, 2026
Interpretation conflict in Fastify @fastify/middie 9.1.0 through 9.3.3 allows remote attackers to bypass path-based access controls. Middie compares path-scoped middleware against the raw request target, while the Fastify router reduces an absolute-form target to its path before dispatch. No authentication or special configuration is required beyond an application relying on path-scoped middie middleware, so protected handlers can expose or modify application data.
Summary
What happened
Interpretation conflict in Fastify @fastify/middie 9.1.0 through 9.3.3 allows remote attackers to bypass path-based access controls. Middie compares path-scoped middleware against the raw request target, while the Fastify router reduces an absolute-form target to its path before dispatch. No authentication or special configuration is required beyond an application relying on path-scoped middie middleware, so protected handlers can expose or modify application data.
The record
- CVE
- CVE-2026-85184
- Published
- Sep 4, 2026
- Updated
- Sep 4, 2026
- Vendor
- Fastify
- Product
- @fastify/middie
- Classifications
- CWE-436, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 4, 2026CVE publishedPublication date reported by the CVE source.
- Sep 4, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=9.1.0 <9.3.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo