CVE-2025-45765: Ruby-JWT Weak Encryption Vulnerability Revealed

Overview

In the ever-evolving landscape of cybersecurity, the discovery of new vulnerabilities is a constant concern. One such vulnerability, CVE-2025-45765, has been identified in the ruby-jwt v3.0.0.beta1 library. This vulnerability stems from weak encryption that could potentially lead to system compromise or data leakage.
The ruby-jwt library is used extensively in web development for JSON Web Token (JWT) authentication-a common method for securely transmitting information between parties as a JSON object. As such, this vulnerability could have far-reaching effects, potentially impacting a multitude of web applications that rely on this library for their security needs.

Vulnerability Summary

CVE ID: CVE-2025-45765
Severity: Critical (9.1 CVSS Score)
Attack Vector: Network
Privileges Required: Low
User Interaction: None
Impact: System Compromise or Data Leakage

Affected Products

Product | Affected Versions

ruby-jwt | v3.0.0.beta1

How the Exploit Works

The vulnerability emerges from the library’s handling of encryption keys. The ruby-jwt v3.0.0.beta1 does not enforce key sizes, leaving it up to the users to ensure the key sizes they choose are secure. This lack of enforcement can lead to the use of weak encryption keys that can be easily broken by attackers, giving them access to sensitive data or even control of the system.

Conceptual Example Code

Here’s a conceptual example of how this vulnerability might be exploited. An attacker could use a brute force attack to uncover the weak encryption key. Once the key is discovered, they can then use it to decode the JWT, gaining access to the sensitive data contained within.

require 'jwt'
weak_key = 'weak_key'
payload = { data: 'Sensitive Information' }
token = JWT.encode payload, weak_key, 'HS256'
puts "Encoded Token: #{token}"
decoded_token = JWT.decode token, weak_key, true, { algorithm: 'HS256' }
puts "Decoded Token: #{decoded_token}"

In this example, the weak_key is easily guessed using brute force methods. Once an attacker has the key, they can easily decode the token and access the sensitive data it was meant to protect.

Mitigation Guidance

Users of the ruby-jwt v3.0.0.beta1 library are strongly advised to apply the vendor patch as soon as possible. In the meantime, protective measures such as using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can provide temporary mitigation. Additionally, users should consider enforcing stronger key sizes within their applications to ensure the integrity and security of their data.