CVE-2021-3729 in Firefly III
Summary
by MITRE • 08/23/2021
firefly-iii is vulnerable to Cross-Site Request Forgery (CSRF)
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Analysis
by VulDB Data Team • 08/26/2021
The firefly-iii web 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 in critical administrative functions. The flaw exists within the application's session management and request processing mechanisms, where legitimate requests are not adequately distinguished from maliciously crafted ones. This vulnerability specifically impacts the application's user account management and financial transaction processing features, potentially enabling attackers to execute unauthorized transfers, modify user settings, or manipulate financial data. The issue represents a fundamental weakness in the application's security architecture that directly violates established web application security principles.
The technical implementation of this CSRF vulnerability occurs when authenticated users visit malicious websites or click on compromised links that trigger unintended actions within the firefly-iii application. The vulnerability manifests because the application fails to validate the referer header or implement anti-CSRF tokens for sensitive operations such as account modifications, transaction creation, or user privilege changes. Attackers can craft malicious requests that leverage the victim's existing authenticated session to perform unauthorized actions without requiring knowledge of the user's credentials. This weakness creates a scenario where the application cannot distinguish between legitimate user-initiated requests and forged requests generated by attackers, effectively bypassing the authentication and authorization controls that should protect sensitive operations.
The operational impact of this vulnerability extends beyond simple data manipulation to potentially compromise the integrity and confidentiality of financial information within the firefly-iii application. An attacker who successfully exploits this CSRF vulnerability could perform unauthorized financial transactions, modify user accounts, or gain elevated privileges within the application. The vulnerability affects all authenticated users and could result in significant financial loss or data breaches depending on the scope of permissions available to compromised accounts. Organizations relying on firefly-iii for personal financial management or small business accounting could face serious consequences including unauthorized fund transfers, data corruption, or complete account compromise. The vulnerability also poses risks to user privacy and could enable attackers to access sensitive financial information through manipulation of the application's data handling processes.
Security mitigations for this CSRF vulnerability should focus on implementing robust anti-CSRF token mechanisms throughout the application's administrative interfaces and sensitive operations. The solution requires incorporating unique, unpredictable tokens for each user session that are validated on the server side before processing any critical requests. Additionally, the application should implement proper referer header validation and utilize the same-origin policy enforcement mechanisms to prevent unauthorized cross-origin requests. Organizations should also consider implementing additional security controls such as request origin validation, double-submit cookie patterns, and comprehensive logging of suspicious activities. These mitigations align with established security standards including CWE-352 for cross-site request forgery and ATT&CK technique T1566 for social engineering attacks that leverage CSRF vulnerabilities. Regular security audits and penetration testing should be conducted to ensure the effectiveness of implemented controls and to identify any additional CSRF-related weaknesses in the application's architecture.