CVE-2024-56331 in uptime-kuma
Summary
by MITRE • 12/20/2024
Uptime Kuma is an open source, self-hosted monitoring tool. An **Improper URL Handling Vulnerability** allows an attacker to access sensitive local files on the server by exploiting the `file:///` protocol. This vulnerability is triggered via the **"real-browser"** request type, which takes a screenshot of the URL provided by the attacker. By supplying local file paths, such as `file:///etc/passwd`, an attacker can read sensitive data from the server. This vulnerability arises because the system does not properly validate or sanitize the user input for the URL field. Specifically: 1. The URL input (``) allows users to input arbitrary file paths, including those using the `file:///` protocol, without server-side validation. 2. The server then uses the user-provided URL to make a request, passing it to a browser instance that performs the "real-browser" request, which takes a screenshot of the content at the given URL. If a local file path is entered (e.g., `file:///etc/passwd`), the browser fetches and captures the file’s content. Since the user input is not validated, an attacker can manipulate the URL to request local files (e.g., `file:///etc/passwd`), and the system will capture a screenshot of the file's content, potentially exposing sensitive data. Any **authenticated user** who can submit a URL in "real-browser" mode is at risk of exposing sensitive data through screenshots of these files. This issue has been addressed in version 1.23.16 and all users are advised to upgrade. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 12/20/2024
The CVE-2024-56331 vulnerability affects Uptime Kuma, an open source self-hosted monitoring tool designed to track the availability and performance of web services. This monitoring solution provides features including real-browser screenshot capabilities that allow administrators to visualize how web pages appear to actual users. The vulnerability stems from improper URL handling within the application's real-browser request functionality, creating a significant security risk that could lead to unauthorized access to sensitive server files. The flaw specifically manifests when users submit URLs through the real-browser mode, which triggers a browser instance to capture screenshots of web content. The vulnerability has been classified as an improper input validation issue that allows attackers to exploit the system's trust in user-provided URLs.
The technical implementation of this vulnerability occurs through the application's lack of proper input sanitization for URL parameters. When a user submits a URL through the real-browser request type, the system does not validate or sanitize the input before passing it to the underlying browser instance. This oversight allows attackers to craft malicious URLs using the file:/// protocol, which bypasses normal web browsing restrictions. The browser instance then processes these local file paths as if they were regular web URLs, effectively enabling file system traversal attacks. The vulnerability is particularly dangerous because it operates at the browser level where the system's security boundaries are normally enforced, allowing the attacker to access sensitive files like /etc/passwd, configuration files, and other system resources that should remain protected from external access. The lack of proper protocol validation means that legitimate file:// URLs are processed without restriction, creating an unrestricted file access vector.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable further attack vectors within the compromised system. Any authenticated user with access to the real-browser functionality can exploit this vulnerability to capture screenshots of sensitive local files, which may contain system credentials, database connection strings, application configuration details, or other confidential information. This threat is particularly concerning in environments where Uptime Kuma is deployed with elevated privileges or where the monitoring tool has access to sensitive network resources. The vulnerability creates a persistent risk for organizations using this monitoring solution, as it can be exploited by both internal users with legitimate access and external attackers who gain authentication credentials through other means. The screenshot capability amplifies the impact because it provides visual confirmation of the compromised data, making it easier for attackers to identify and exploit valuable information. This vulnerability directly relates to CWE-20, Improper Input Validation, and can be mapped to ATT&CK technique T1083 (File and Directory Discovery) and T1566 (Phishing).
The mitigation for CVE-2024-56331 requires immediate action to upgrade to version 1.23.16 or later, which includes proper URL validation and sanitization mechanisms. Organizations should implement additional controls including restricting access to the real-browser functionality to only trusted users, implementing network segmentation to limit the exposure of sensitive systems, and monitoring for unusual URL patterns in system logs. The vulnerability cannot be effectively mitigated through workarounds since it stems from fundamental input validation failures within the core application logic. Security teams should also consider implementing automated monitoring for file:// protocol usage in their network traffic and application logs to detect potential exploitation attempts. The fix implemented in version 1.23.16 addresses the root cause by adding proper validation to ensure that URLs containing file protocols are either rejected or properly sanitized before being processed by the browser instance, thereby preventing unauthorized access to local files while maintaining the legitimate functionality of the monitoring tool.