Description

Missing Authorization vulnerability in DimaFreund Rentsyst allows Exploiting Incorrectly Configured Access Control Security Levels. This issue affects Rentsyst: from n/a through 2.1.2.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "5.3",
  "pubDate": "2026-09-02T12:17:18.010Z",
  "pubdate": "2026-09-02T12:17:18.010Z",
  "executiveSummary": "A missing authorization vulnerability has been identified in the Rentsyst platform, impacting all versions from n/a through 2.1.2. The vulnerability stems from incorrectly configured access control security levels, which allows unauthorized users to perform actions restricted to higher-privileged accounts.\nThis vulnerability is categorized as a failure in authorization enforcement, typically associated with CWE-862 (Missing Authorization). The impact is significant, as it permits attackers to bypass intended security constraints, potentially leading to unauthorized data access, manipulation of rental management workflows, or administrative command execution.\nThe vulnerability does not require complex exploitation techniques; instead, it leverages the system's failure to validate the user's privilege level against the requested resource or function. An attacker with a standard low-privileged account or, in some configurations, an unauthenticated actor, could invoke sensitive API endpoints or server-side functions by simply manipulating request parameters or bypassing front-end UI restrictions.\nGiven that Rentsyst is used for fleet and rental management, the risk implications include exposure of sensitive customer data, financial record tampering, and disruption of rental operations. Organizations utilizing the affected versions should prioritize access control audits and implement strict server-side authorization checks for all administrative and user-specific functions.",
  "technicalDetails": "The vulnerability resides within the core access control layer of Rentsyst (versions 2.1.2 and earlier), where the application logic fails to perform a consistent authorization check on incoming requests. Specifically, the software relies on insecure access control security levels that are either not enforced at the controller level or are easily bypassed due to faulty middleware implementation.\nRoot Cause Analysis: The underlying flaw is the omission of server-side authorization verification for restricted function calls. While the client-side interface may hide certain options from unauthorized users, the backend fails to validate that the authenticated session possesses the mandatory permissions required to interact with the target resource. Consequently, the application assumes that any request directed at an administrative or restricted function is authorized if the session cookie or token is present, regardless of the user's role.\nExploitation Method: An attacker can exploit this by identifying the specific API endpoints or internal functions responsible for privileged actions. Since the backend lacks proper access control decorators or authorization guards, an attacker can directly craft HTTP requests (e.g., GET, POST, PUT, DELETE) directed at these sensitive endpoints. By observing the application's traffic, an attacker can enumerate hidden resources and identify the request structure necessary to execute privileged commands. Because the vulnerability is a failure of server-side logic, no front-end obfuscation can prevent the request from being processed.\nAttack Flow: 1. Reconnaissance: The attacker intercepts legitimate application traffic to identify patterns in API requests, specifically looking for endpoints that handle user administration, configuration changes, or sensitive data modification. 2. Request Modification: The attacker attempts to access these identified endpoints while logged in as a lower-privileged user. 3. Bypassing Controls: Because the server-side controller fails to check user permissions (CWE-862), the server executes the requested action without verifying if the user has the 'Admin' or 'Manager' role. 4. Execution: The server processes the request as if it were a legitimate administrative command, granting the attacker unauthorized control over the system's business logic or database entries.\nPost-Exploitation Impact: Successful exploitation results in complete bypass of role-based access control (RBAC). This may allow attackers to escalate their privileges, modify configuration settings, delete or exfiltrate rental data, and perform administrative operations that compromise the integrity and confidentiality of the entire Rentsyst deployment."
}