Fastify: Security Vulnerabilities
Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.3, a denial-of-service vulnerability in Fastify’s Web Streams response handling can allow a remote client to exhaust server memory. Applications that return a ReadableStream (or Response with a Web Stream body) via reply.send() are impacted. A slow or non-reading client can trigger unbounded buffering when backpressure is ignored, leading to process crashes or severe degradation. This issue has been patched in version 5.7.3.
CVSS Score
3.7
EPSS Score
0.005
Published
2026-02-03
@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.
CVSS Score
8.4
EPSS Score
0.005
Published
2026-01-19
fastify-reply-from is a Fastify plugin to forward the current HTTP request to another server. Prior to 12.5.0, by crafting a malicious URL, an attacker could access routes that are not allowed, even though the reply.from is defined for specific routes in @fastify/reply-from. This vulnerability is fixed in 12.5.0.
CVSS Score
6.9
EPSS Score
0.002
Published
2025-12-01
Fastify is a fast and low overhead web framework, for Node.js. In versions 5.0.0 to 5.3.0 as well as version 4.29.0, applications that specify different validation strategies for different content types have a possibility to bypass validation by providing a _slightly altered_ content type such as with different casing or altered whitespacing before `;`. This was patched in v5.3.1, but the initial patch did not cover all problems. This has been fully patched in v5.3.2 and v4.29.1. A workaround involves not specifying individual content types in the schema.
CVSS Score
7.5
EPSS Score
0.007
Published
2025-04-18
fastify-reply-from is a Fastify plugin to forward the current HTTP request to another server. A reverse proxy server built with `@fastify/reply-from` could misinterpret the incoming body by passing an header `ContentType: application/json ; charset=utf-8`. This can lead to bypass of security checks. This vulnerability has been patched in '@fastify/reply-from` version 9.6.0.
CVSS Score
5.3
EPSS Score
0.005
Published
2024-01-08
All versions of @fastify/oauth2 used a statically generated state parameter at startup time and were used across all requests for all users. The purpose of the Oauth2 state parameter is to prevent Cross-Site-Request-Forgery attacks. As such, it should be unique per user and should be connected to the user's session in some way that will allow the server to validate it.
v7.2.0 changes the default behavior to store the state in a cookie with the http-only and same-site=lax attributes set. The state is now by default generated for every user. Note that this contains a breaking change in the checkStateFunction function, which now accepts the full Request object.
CVSS Score
8.8
EPSS Score
0.007
Published
2023-07-04
@fastify/passport is a port of passport authentication library for the Fastify ecosystem. Applications using `@fastify/passport` in affected versions for user authentication, in combination with `@fastify/session` as the underlying session management mechanism, are vulnerable to session fixation attacks from network and same-site attackers. fastify applications rely on the `@fastify/passport` library for user authentication. The login and user validation are performed by the `authenticate` function. When executing this function, the `sessionId` is preserved between the pre-login and the authenticated session. Network and same-site attackers can hijack the victim's session by tossing a valid `sessionId` cookie in the victim's browser and waiting for the victim to log in on the website. As a solution, newer versions of `@fastify/passport` regenerate `sessionId` upon login, preventing the attacker-controlled pre-session cookie from being upgraded to an authenticated session. Users are advised to upgrade. There are no known workarounds for this vulnerability.
CVSS Score
8.1
EPSS Score
0.008
Published
2023-04-21
@fastify/passport is a port of passport authentication library for the Fastify ecosystem. The CSRF (Cross-Site Request Forger) protection enforced by the `@fastify/csrf-protection` library, when combined with `@fastify/passport` in affected versions, can be bypassed by network and same-site attackers. `fastify/csrf-protection` implements the synchronizer token pattern (using plugins `@fastify/session` and `@fastify/secure-session`) by storing a random value used for CSRF token generation in the `_csrf` attribute of a user's session. The `@fastify/passport` library does not clear the session object upon authentication, preserving the `_csrf` attribute between pre-login and authenticated sessions. Consequently, CSRF tokens generated before authentication are still valid. Network and same-site attackers can thus obtain a CSRF token for their pre-session, fixate that pre-session in the victim's browser via cookie tossing, and then perform a CSRF attack after the victim authenticates. As a solution, newer versions of `@fastify/passport` include the configuration options: `clearSessionOnLogin (default: true)` and `clearSessionIgnoreFields (default: ['passport', 'session'])` to clear all the session attributes by default, preserving those explicitly defined in `clearSessionIgnoreFields`.
CVSS Score
6.5
EPSS Score
0.004
Published
2023-04-21
@fastify/csrf-protection is a plugin which helps protect Fastify servers against CSRF attacks. The CSRF protection enforced by the @fastify/csrf-protection library in combination with @fastify/cookie can be bypassed from network and same-site attackers under certain conditions. @fastify/csrf-protection supports an optional userInfo parameter that binds the CSRF token to the user. This parameter has been introduced to prevent cookie-tossing attacks as a fix for CVE-2021-29624. Whenever userInfo parameter is missing, or its value can be predicted for the target user account, network and same-site attackers can 1. fixate a _csrf cookie in the victim's browser, and 2. forge CSRF tokens that are valid for the victim's session. This allows attackers to bypass the CSRF protection mechanism. As a fix, @fastify/csrf-protection starting from version 6.3.0 (and v4.1.0) includes a server-defined secret hmacKey that cryptographically binds the CSRF token to the value of the _csrf cookie and the userInfo parameter, making tokens non-spoofable by attackers. This protection is effective as long as the userInfo parameter is unique for each user. This is patched in versions 6.3.0 and v4.1.0. Users are advised to upgrade. Users unable to upgrade may use a random, non-predictable userInfo parameter for each user as a mitigation.
CVSS Score
5.3
EPSS Score
0.003
Published
2023-04-20
@fastify/multipart is a Fastify plugin to parse the multipart content-type. Prior to versions 7.4.1 and 6.0.1, @fastify/multipart may experience denial of service due to a number of situations in which an unlimited number of parts are accepted. This includes the multipart body parser accepting an unlimited number of file parts, the multipart body parser accepting an unlimited number of field parts, and the multipart body parser accepting an unlimited number of empty parts as field parts. This is fixed in v7.4.1 (for Fastify v4.x) and v6.0.1 (for Fastify v3.x). There are no known workarounds.
CVSS Score
7.5
EPSS Score
0.015
Published
2023-02-14