// For flags

CVE-2023-27495

Bypass of CSRF protection in the presence of predictable userInfo in @fastify/csrf-protection

Severity Score

6.5
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

-
*SSVC
Descriptions

@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.

*Credits: N/A
CVSS Scores
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None
* Common Vulnerability Scoring System
SSVC
  • Decision:-
Exploitation
-
Automatable
-
Tech. Impact
-
* Organization's Worst-case Scenario
Timeline
  • 2023-03-01 CVE Reserved
  • 2023-04-20 CVE Published
  • 2024-08-02 CVE Updated
  • 2024-11-10 EPSS Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-352: Cross-Site Request Forgery (CSRF)
CAPEC
Affected Vendors, Products, and Versions
Vendor Product Version Other Status
Vendor Product Version Other Status <-- --> Vendor Product Version Other Status
Fastify
Search vendor "Fastify"
Csrf-protection
Search vendor "Fastify" for product "Csrf-protection"
< 4.1.0
Search vendor "Fastify" for product "Csrf-protection" and version " < 4.1.0"
node.js
Affected
Fastify
Search vendor "Fastify"
Csrf-protection
Search vendor "Fastify" for product "Csrf-protection"
>= 5.0.0 < 6.3.0
Search vendor "Fastify" for product "Csrf-protection" and version " >= 5.0.0 < 6.3.0"
node.js
Affected