kkFileView Server-Side-Request-Forgery Scanner

kkFileView is a file viewing software primarily used in corporate environments to enable document sharing and collaboration. It is commonly utilized by businesses for its ability to support a wide range of document formats, allowing users to view files without needing to download them. kkFileView is developed by Keking and is popular for its easy integration with other web applications and document management systems. Its functionalities are especially beneficial for large enterprises where secure document access and external display are important. The software is available as a self-hosted application, thus offering scalability tailored to business needs. The flexibility of customizing its appearance and functionalities makes it a widely adopted solution for document handling and previewing.

Server-Side Request Forgery (SSRF) is a vulnerability that allows an attacker to induce the server-side application to make unauthorized HTTP requests. This vulnerability occurs when a web application fetches a resource without validating the user-supplied URL. In kkFileView, SSRF could enable an attacker to trigger requests to internal systems or external endpoints as the vulnerable server, possibly bypassing access restrictions. It can be exploited to access internal administrative interfaces that are not disclosed to the public, leading to sensitive data exposure. Moreover, SSRF can be employed to interact with third-party services, manipulate data, and conduct network vulnerability scanning. This vulnerability poses a significant threat to the confidentiality, integrity, and availability of system data.

The technical vulnerability in kkFileView involves a specific endpoint /onlinePreview, which accepts user-provided URLs without sufficient validation. An attacker can exploit this by encoding malicious URLs in base64 format, which, when processed by the application, triggers unintended requests. This endpoint does not suitably sanitize input leading to SSRF vulnerabilities. By manipulating the URL parameter, attackers can direct the server to interact with internal resources or unauthorized external targets. This inadequately filtered input enables the possibility of access to sensitive information, compromising the security of the application environment. Such flaws highlight the necessity of implementing robust input validation in URL handling to prevent exploitation.

Exploitation of SSRF vulnerabilities in kkFileView could lead to severe consequences such as unauthorized access to sensitive internal systems. An attacker might gain insights into the server's network architecture and manipulate internal data. Additionally, this flaw could be utilized for exfiltrating data, causing information leaks, or escalating privileges within the compromised environment. The potential for the server to be misused in further attacks, such as port scanning or other network-based exploitation techniques, exists. Organizations could face considerable reputational damage and financial losses resulting from data breaches or service disruptions.

REFERENCES

• https://github.com/kekingcn/kkFileView/issues/296