CVE-2022-31535 in Fishtank
Summary
by MITRE • 07/11/2022
The freefood89/Fishtank repository through 2015-06-24 on GitHub allows absolute path traversal because the Flask send_file function is used unsafely.
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Analysis
by VulDB Data Team • 07/20/2022
The vulnerability identified as CVE-2022-31535 resides within the freefood89/Fishtank repository, a web application built using the Flask framework. This repository, which was last updated on June 24, 2015, contains a critical security flaw that enables attackers to perform absolute path traversal attacks. The vulnerability specifically stems from the improper usage of Flask's send_file function, which is designed to serve files from the server to clients. When this function is invoked with user-controllable input without proper validation or sanitization, it creates an opportunity for malicious actors to access files outside the intended directory structure. The flaw represents a classic example of insecure file handling that can lead to unauthorized data access and potential system compromise.
The technical implementation of this vulnerability occurs when the application accepts file paths from user input and directly passes them to Flask's send_file function without adequate security checks. This allows attackers to manipulate the file path parameter to traverse the file system hierarchy and access sensitive files that should remain protected. The attack vector typically involves crafting malicious URLs with directory traversal sequences such as ../ or ../../ that bypass normal file access restrictions. When the Flask application processes these requests, it attempts to serve files from locations specified by the attacker, potentially exposing system files, configuration data, or other sensitive information. This weakness aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The vulnerability demonstrates a fundamental flaw in input validation and file access control mechanisms within the web application.
The operational impact of this vulnerability extends beyond simple information disclosure, potentially enabling more severe attacks such as remote code execution or complete system compromise. An attacker who successfully exploits this vulnerability can gain access to sensitive files including database credentials, application configuration files, source code repositories, and system configuration data. The exposure of such information can facilitate further attacks within the network infrastructure, allowing for privilege escalation or lateral movement. This type of vulnerability is particularly dangerous in web applications where user input is not properly sanitized, as it provides attackers with a direct pathway to access the underlying file system. The long-term implications include potential data breaches, regulatory compliance violations, and reputational damage to organizations that may have deployed vulnerable versions of the software. The vulnerability also aligns with several tactics described in the MITRE ATT&CK framework, particularly those related to privilege escalation and credential access, as attackers can leverage the exposed files to obtain sensitive information that could be used for further exploitation.
Mitigation strategies for this vulnerability must address both the immediate security flaw and implement comprehensive input validation measures. The primary remediation involves modifying the application code to sanitize all user inputs before passing them to the Flask send_file function. This includes implementing proper path validation, using whitelist-based file access controls, and ensuring that file paths are resolved within a designated safe directory. Organizations should also consider implementing additional security measures such as input parameter validation, secure coding practices, and regular security audits. The fix requires developers to avoid direct user input handling in file access operations and instead implement proper abstraction layers that validate and normalize file paths before processing. Implementing proper access controls and restricting file system access to only necessary operations can significantly reduce the attack surface. Additionally, organizations should conduct regular security assessments and penetration testing to identify similar vulnerabilities in other applications and ensure that secure coding practices are consistently applied throughout the software development lifecycle. The remediation process should also include monitoring and logging of file access operations to detect potential exploitation attempts and maintain audit trails for security investigations.