CVE-2020-35217 in Web Framework
Summary
by MITRE • 01/20/2021
Vert.x-Web framework v4.0 milestone 1-4 does not perform a correct CSRF verification. Instead of comparing the CSRF token in the request with the CSRF token in the cookie, it compares the CSRF token in the cookie against a CSRF token that is stored in the session. An attacker does not even need to provide a CSRF token in the request because the framework does not consider it. The cookies are automatically sent by the browser and the verification will always succeed, leading to a successful CSRF attack.
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Analysis
by VulDB Data Team • 02/18/2021
The CVE-2020-35217 vulnerability represents a critical flaw in the Vert.x-Web framework version 4.0 milestone 1 through 4, specifically affecting the Cross-Site Request Forgery protection mechanism. This vulnerability stems from a fundamental misimplementation of CSRF token validation logic where the framework fails to properly verify the integrity of the authentication process. The flaw occurs at the core of the framework's security controls, where the expected behavior should validate that the token submitted in the request matches the token stored in the user's session, but instead performs an incorrect comparison operation. This misconfiguration creates a complete bypass of the CSRF protection mechanism, rendering the security feature ineffective against malicious attacks.
The technical implementation error manifests in how the framework handles token verification within the HTTP request processing pipeline. When a user makes a request, the framework should extract the CSRF token from the request headers or form data and compare it against the token stored in the session. However, the vulnerable implementation incorrectly compares the token stored in the session against the token present in the cookie, rather than the token submitted by the user. This fundamental logic error means that the framework accepts any request that contains a valid cookie, regardless of whether the request includes a proper CSRF token. The attacker can simply make a request with a valid session cookie and no CSRF token, and the framework will accept the request as legitimate, completely bypassing the security check.
This vulnerability has severe operational implications for applications built using the affected Vert.x-Web framework versions, as it allows attackers to execute unauthorized actions on behalf of authenticated users. The attack vector leverages the automatic cookie submission behavior of web browsers, where the framework's flawed validation logic treats any valid session cookie as sufficient authentication. This creates a scenario where an attacker can craft malicious requests that appear to originate from legitimate authenticated users, enabling them to perform actions such as changing user passwords, modifying account settings, or executing financial transactions. The impact extends beyond simple session hijacking to encompass any functionality that relies on CSRF protection, making it particularly dangerous for applications handling sensitive user data or financial operations.
The vulnerability aligns with CWE-352, which specifically addresses Cross-Site Request Forgery weaknesses in software implementations. This classification emphasizes the fundamental flaw in the framework's design where the security mechanism is fundamentally broken rather than merely misconfigured. From an ATT&CK perspective, this vulnerability maps to technique T1531, which involves the use of valid credentials to perform unauthorized actions, as the framework accepts requests with valid session cookies without proper token validation. The attack surface is particularly concerning because it requires no special privileges or advanced techniques from the attacker, making it accessible to threat actors with basic web application exploitation knowledge. The vulnerability also demonstrates poor security by design principles, where the framework's developers failed to properly validate the expected behavior of their CSRF protection mechanism. Organizations using affected versions should immediately implement mitigations including upgrading to patched versions, implementing additional security controls, or manually patching the framework components to correct the token validation logic. The remediation process should include thorough testing to ensure that the corrected implementation properly validates CSRF tokens in requests while maintaining proper session management functionality.