CVE-2026-22031
Fastify Middie Middleware Path Bypass
Description
@fastify/middie is the plugin that adds middleware support on steroids to Fastify. A security vulnerability exists in @fastify/middie prior to version 9.1.0 where middleware registered with a specific path prefix can be bypassed using URL-encoded characters (e.g., `/%61dmin` instead of `/admin`). While the middleware engine fails to match the encoded path and skips execution, the underlying Fastify router correctly decodes the path and matches the route handler, allowing attackers to access protected endpoints without the middleware constraints. Version 9.1.0 fixes the issue.
INFO
Published Date :
Jan. 19, 2026, 4:15 p.m.
Last Modified :
March 13, 2026, 2:40 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | MITRE-CVE | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update @fastify/middie to version 9.1.0 or later.
- Ensure URL decoding is handled consistently.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-22031.
| URL | Resource |
|---|---|
| https://github.com/fastify/middie/commit/d44cd56eb724490babf7b452fdbbdd37ea2effba | Patch |
| https://github.com/fastify/middie/pull/245 | Issue Tracking Patch |
| https://github.com/fastify/middie/releases/tag/v9.1.0 | Product Release Notes |
| https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p | Exploit Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-22031 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-22031
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-22031 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-22031 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Mar. 13, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Added CPE Configuration OR *cpe:2.3:a:openjsf:@fastify/middie:*:*:*:*:*:fastify:*:* versions up to (excluding) 9.1.0 Added Reference Type GitHub, Inc.: https://github.com/fastify/middie/commit/d44cd56eb724490babf7b452fdbbdd37ea2effba Types: Patch Added Reference Type GitHub, Inc.: https://github.com/fastify/middie/pull/245 Types: Issue Tracking, Patch Added Reference Type GitHub, Inc.: https://github.com/fastify/middie/releases/tag/v9.1.0 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p Types: Exploit, Vendor Advisory -
New CVE Received by [email protected]
Jan. 19, 2026
Action Type Old Value New Value Added Description @fastify/middie is the plugin that adds middleware support on steroids to Fastify. A security vulnerability exists in @fastify/middie prior to version 9.1.0 where middleware registered with a specific path prefix can be bypassed using URL-encoded characters (e.g., `/%61dmin` instead of `/admin`). While the middleware engine fails to match the encoded path and skips execution, the underlying Fastify router correctly decodes the path and matches the route handler, allowing attackers to access protected endpoints without the middleware constraints. Version 9.1.0 fixes the issue. Added CVSS V3.1 AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L Added CWE CWE-177 Added Reference https://github.com/fastify/middie/commit/d44cd56eb724490babf7b452fdbbdd37ea2effba Added Reference https://github.com/fastify/middie/pull/245 Added Reference https://github.com/fastify/middie/releases/tag/v9.1.0 Added Reference https://github.com/fastify/middie/security/advisories/GHSA-cxrg-g7r8-w69p