CVE-2024-37893 in Firefly III
Summary
by MITRE • 06/17/2024
Firefly III is a free and open source personal finance manager. In affected versions an MFA bypass in the Firefly III OAuth flow may allow malicious users to bypass the MFA-check. This allows malicious users to use password spraying to gain access to Firefly III data using passwords stolen from other sources. As OAuth applications are easily enumerable using an incrementing id, an attacker could try sign an OAuth application up to a users profile quite easily if they have created one. The attacker would also need to know the victims username and password. This problem has been patched in Firefly III v6.1.17 and up. Users are advised to upgrade. Users unable to upgrade should Use a unique password for their Firefly III instance and store their password securely, i.e. in a password manager.
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Analysis
by VulDB Data Team • 06/21/2024
The vulnerability identified as CVE-2024-37893 affects Firefly III, a widely used free and open source personal finance management application. This security flaw represents a critical authentication bypass issue within the application's OAuth implementation that significantly weakens the overall security posture of user accounts. The vulnerability specifically targets the multi-factor authentication mechanism during the OAuth flow, creating a pathway for unauthorized access that bypasses the intended security controls. The flaw exists in versions prior to v6.1.17, leaving users of older releases exposed to potential exploitation.
The technical nature of this vulnerability stems from an insufficient validation mechanism within the OAuth authentication process that allows malicious actors to circumvent the multi-factor authentication requirements. This occurs during the OAuth application registration and authentication flow where the system fails to properly enforce MFA checks for users who have enabled this security feature. The vulnerability creates a scenario where an attacker can exploit the OAuth application enumeration capability, as these applications can be easily discovered through simple ID incrementation techniques. This enumeration capability combined with the MFA bypass creates a particularly dangerous attack vector for credential stuffing and password spraying operations.
The operational impact of this vulnerability is substantial as it enables attackers to perform password spraying attacks against Firefly III user accounts without being blocked by MFA requirements. Attackers can leverage stolen credentials from other sources and attempt to gain access to personal financial data by exploiting the OAuth application enumeration feature. The combination of knowing a victim's username and password, along with the ability to enumerate OAuth applications, creates a successful attack scenario that could lead to unauthorized access to sensitive financial information. This vulnerability directly violates security principles outlined in CWE-305, which addresses authentication bypass mechanisms, and aligns with ATT&CK technique T1110.003 for credential stuffing attacks.
The security implications extend beyond simple unauthorized access as personal financial data becomes vulnerable to exposure and potential manipulation. The vulnerability essentially undermines the security controls that users rely upon to protect their financial information, making it easier for threat actors to compromise user accounts. Organizations and individuals using Firefly III should immediately implement the recommended mitigation measures including upgrading to version 6.1.17 or later. For users unable to upgrade immediately, the recommendation to use unique passwords and store them securely in password managers provides essential protection against exploitation attempts. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date security practices and the potential consequences of authentication bypass flaws in financial applications.