CVE-2021-21246 in OneDev
Summary
by MITRE • 01/16/2021
OneDev is an all-in-one devops platform. In OneDev before version 4.0.3, the REST UserResource endpoint performs a security check to make sure that only administrators can list user details. However for the `/users/{id}` endpoint there are no security checks enforced so it is possible to retrieve arbitrary user details including their Access Tokens! These access tokens can be used to access the API or clone code in the build spec via the HTTP(S) protocol. It has permissions to all projects accessible by the user account. This issue may lead to `Sensitive data leak` and leak the Access Token which can be used to impersonate the administrator or any other users. This issue was addressed in 4.0.3 by removing user info from restful api.
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Analysis
by VulDB Data Team • 02/15/2021
The vulnerability described in CVE-2021-21246 affects OneDev, an all-in-one DevOps platform, and represents a critical authorization flaw that undermines the system's security model. This issue stems from an inconsistent security implementation within the platform's REST API endpoints, where administrative protections are applied selectively to different API routes. The vulnerability exists in versions prior to 4.0.3 and demonstrates a classic case of improper access control where the system fails to properly validate user permissions across all endpoints, creating a pathway for unauthorized data extraction.
The technical flaw manifests in the inconsistent enforcement of security checks across the UserResource API endpoints. While the `/users` endpoint correctly implements administrative authorization checks to prevent unauthorized users from listing user details, the `/users/{id}` endpoint lacks these protective measures entirely. This design inconsistency allows authenticated users to exploit the API by directly accessing specific user records through their IDs, bypassing the intended authorization controls. The vulnerability is particularly dangerous because it enables the retrieval of sensitive user information including access tokens, which serve as the primary means of authentication within the platform's API ecosystem.
The operational impact of this vulnerability extends far beyond simple data leakage, representing a significant risk to the entire DevOps infrastructure. An attacker who discovers this vulnerability can obtain access tokens that provide full programmatic access to the API and code repositories through HTTP(S) protocols. These tokens grant permissions to all projects accessible by the compromised user account, potentially allowing for complete system compromise. The access tokens can be used to clone code repositories, execute builds, modify configurations, and perform other privileged operations that would normally be restricted to authorized administrators. This creates a scenario where an attacker can impersonate any user account within the system, including high-privilege administrators, leading to complete unauthorized access to the entire DevOps platform.
This vulnerability aligns with CWE-284, which describes improper access control in software systems, and represents a clear violation of the principle of least privilege. The security flaw enables what is known as a privilege escalation attack, where a user with minimal privileges can gain access to sensitive information and capabilities that should be restricted. From an ATT&CK framework perspective, this vulnerability maps to T1566 (Phishing for Information) and T1078 (Valid Accounts) as attackers can leverage stolen tokens to maintain persistent access to the system. The issue also relates to T1003 (OS Credential Dumping) and T1528 (Gather Victim Identity Information) as it facilitates the extraction of authentication credentials and user identity data. The remediation implemented in version 4.0.3 by removing user information from the RESTful API represents a proper defensive measure that eliminates the data exposure vector entirely, demonstrating the importance of consistent security controls across all API endpoints.
Organizations using OneDev should immediately upgrade to version 4.0.3 or later to address this vulnerability, while also implementing monitoring for unauthorized API access attempts and token usage patterns. Security teams should conduct thorough reviews of their API endpoint access controls to identify similar inconsistencies that could lead to comparable vulnerabilities. The incident highlights the critical importance of maintaining consistent security policies across all system interfaces and the necessity of comprehensive testing to ensure that access controls are properly enforced at every API endpoint. Additionally, organizations should implement token rotation policies and monitor for unusual access patterns that could indicate exploitation of similar authorization flaws.