CVE-2021-21269 in Keymaker
Summary
by MITRE • 01/20/2021
Keymaker is a Mastodon Community Finder based Matrix Community serverlist page Server. In Keymaker before version 0.2.0, the assets endpoint did not check for the extension. The rust `join` method without checking user input might have made it abe to do a Path Traversal attack causing to read more files than allowed. This is fixed in version 0.2.0.
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Analysis
by VulDB Data Team • 02/18/2021
The vulnerability identified as CVE-2021-21269 affects Keymaker, a Mastodon Community Finder application that operates as a Matrix Community serverlist page server. This application serves as a bridge between Mastodon instances and Matrix communities, facilitating discovery and connection between decentralized social networks. The security flaw resides within the assets endpoint handling mechanism, which represents a critical weakness in the application's file access controls and input validation processes. The vulnerability specifically impacts versions prior to 0.2.0, indicating that the developers recognized and addressed this issue in their subsequent release.
The technical flaw manifests through the improper implementation of the rust join method, which fails to validate file extensions or sanitize user inputs before processing file paths. This implementation pattern creates a path traversal attack vector where malicious actors can manipulate input parameters to access files beyond the intended asset directories. The rust join method, when used without proper input validation, allows attackers to construct malicious file paths that can traverse directory structures and access sensitive files that should remain protected. This type of vulnerability directly maps to CWE-22 Path Traversal and CWE-77 Path Traversal in the Common Weakness Enumeration catalog, which categorizes these issues under the broader family of directory traversal attacks.
The operational impact of this vulnerability is significant, as it could potentially allow remote attackers to access sensitive files on the server hosting Keymaker. Attackers could exploit this weakness to read configuration files, database credentials, application source code, or other confidential data stored on the same system. The severity of this exposure depends on the server's file system structure and the sensitivity of files accessible through the application's asset directory. This vulnerability represents a critical security risk for any organization relying on Keymaker for community discovery services, as it could lead to data breaches, system compromise, or unauthorized access to sensitive information. The attack surface expands beyond just the application itself to include any files accessible through the server's file system that might be reachable through the vulnerable path traversal mechanism.
The fix implemented in version 0.2.0 addresses this vulnerability by properly validating file extensions and sanitizing user inputs before processing file paths through the rust join method. This mitigation approach aligns with established security practices for preventing path traversal attacks, including input validation, proper file path handling, and ensuring that file access operations are restricted to intended directories. Organizations using Keymaker should immediately upgrade to version 0.2.0 or later to remediate this vulnerability. The solution demonstrates the importance of proper input validation and secure coding practices in preventing directory traversal attacks, which are commonly exploited in web application security breaches. This vulnerability also aligns with ATT&CK technique T1083 File and Directory Discovery, which describes methods attackers use to enumerate files and directories on compromised systems. The remediation process emphasizes the need for secure coding standards and proper validation of all user inputs, particularly when handling file system operations in web applications.