CVE-2021-3900 in Firefly III
Summary
by MITRE • 10/27/2021
firefly-iii is vulnerable to Cross-Site Request Forgery (CSRF)
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Analysis
by VulDB Data Team • 11/01/2021
The firefly-iii application presents a critical cross-site request forgery vulnerability that allows attackers to perform unauthorized actions on behalf of authenticated users. This vulnerability stems from the application's insufficient validation of request origins and lack of proper anti-CSRF token implementation within its web interface. The flaw exists in the application's handling of state-changing requests that modify user data or system configurations, making it susceptible to exploitation through maliciously crafted web pages or emails that trick users into performing unintended operations.
The technical implementation of this CSRF vulnerability demonstrates a failure in the application's security controls as defined by CWE-352, which specifically addresses cross-site request forgery conditions. The vulnerability occurs when the application accepts requests without validating that they originate from legitimate sources within the same site context. Attackers can exploit this by crafting malicious HTML pages that automatically submit requests to the firefly-iii application, potentially leading to unauthorized transactions, data modifications, or account manipulations. The absence of proper CSRF tokens or origin validation mechanisms creates an environment where attackers can leverage user sessions to execute malicious operations without their knowledge or consent.
The operational impact of this vulnerability extends beyond simple data manipulation to encompass potential financial losses and unauthorized access to sensitive user information. An attacker could craft targeted campaigns to exploit authenticated sessions, potentially transferring funds, modifying user preferences, or creating unauthorized entries within the financial tracking system. This vulnerability particularly affects the application's core functionality as users rely on firefly-iii for managing their financial data, making successful exploitation potentially devastating for individual users and organizations that depend on the platform. The vulnerability also aligns with ATT&CK technique T1566 which describes social engineering tactics used to gain initial access through malicious links or content.
Mitigation strategies for this CSRF vulnerability should focus on implementing robust anti-CSRF mechanisms including the generation and validation of unique tokens for each user session, proper origin checking of requests, and the enforcement of strict validation controls for all state-changing operations. Organizations should ensure that all forms and API endpoints that modify application state require proper CSRF token verification before processing requests. The implementation should follow established security best practices including the use of secure, random tokens that are tied to specific user sessions and validated on the server side. Additionally, developers should consider implementing Content Security Policy headers and other defensive measures to further reduce the attack surface. Regular security testing and code reviews should be conducted to identify similar vulnerabilities and ensure that CSRF protection mechanisms remain effective against evolving attack techniques.