CVE-2026-40865: Horilla HRMS Auth Bypass Vulnerability

CVE-2026-40865 Overview

CVE-2026-40865 is an Insecure Direct Object Reference (IDOR) vulnerability affecting Horilla, an open source Human Resource Management System (HRMS). The vulnerability exists in the employee document viewer functionality, where any authenticated user can access other employees' uploaded documents by simply manipulating the document ID parameter in the request. This exposes sensitive HR files including identity documents, employment contracts, certificates, and other private employee records.

Critical Impact

Authenticated attackers can access confidential HR documents belonging to any employee in the system, potentially exposing personally identifiable information (PII), contracts, and sensitive credentials.

Affected Products

• Horilla HRMS version 1.5.0

Discovery Timeline

• 2026-04-21 - CVE CVE-2026-40865 published to NVD
• 2026-04-22 - Last updated in NVD database

Technical Details for CVE-2026-40865

Vulnerability Analysis

This Insecure Direct Object Reference vulnerability stems from improper access control implementation in the employee document viewer component of Horilla HRMS. When an authenticated user requests to view their uploaded documents, the application passes a document ID as a parameter. The application fails to verify whether the requesting user has authorization to access the specified document, relying solely on the document ID without validating ownership or permissions.

The vulnerability allows horizontal privilege escalation, where a regular authenticated employee can access documents belonging to other employees at the same or different authorization levels. The attack requires only network access and low-privileged authentication, making it relatively easy to exploit.

Root Cause

The root cause is classified as CWE-284 (Improper Access Control). The Horilla HRMS application does not implement proper authorization checks when serving employee documents. Instead of verifying that the authenticated user owns or has legitimate access to the requested document, the system blindly serves any document based solely on the provided document ID parameter.

This design flaw creates a direct mapping between user-controlled input (document ID) and sensitive resources without an intervening authorization layer. The missing ownership validation allows any authenticated user to enumerate and access documents across the entire system.

Attack Vector

The attack is network-based and requires only low-level authentication. An attacker with a valid employee account can exploit this vulnerability by:

1. Authenticating to the Horilla HRMS application with any valid employee credentials
2. Navigating to the document viewer functionality to observe legitimate document requests
3. Identifying the document ID parameter in the request (typically a sequential or predictable identifier)
4. Modifying the document ID value to reference documents belonging to other employees
5. Iterating through document IDs to systematically harvest sensitive employee documents

The exploitation is straightforward and does not require user interaction or special conditions. Once exploited, attackers gain read access to confidential employee records including identity documents, contracts, and certificates stored in the HRMS.

Detection Methods for CVE-2026-40865

Indicators of Compromise

• Unusual patterns of document access requests from a single user account accessing multiple employee IDs
• Sequential or enumerated document ID requests in web application logs
• Access attempts to documents outside the authenticated user's department or authorization scope
• High volume of document viewer requests from the same session in a short time period

Detection Strategies

• Implement web application firewall (WAF) rules to detect sequential or enumerated parameter manipulation
• Configure application logging to capture document access events with user context and document ownership information
• Deploy user behavior analytics (UBA) to identify abnormal document access patterns
• Review web server access logs for requests to the document viewer endpoint with varied document ID parameters

Monitoring Recommendations

• Enable detailed access logging for the document viewer functionality including user ID, document ID, and document owner
• Establish baseline document access patterns per user role and alert on deviations
• Monitor for bulk document access attempts or rapid sequential requests from single sessions
• Integrate HRMS application logs with SIEM platform for correlation and alerting

How to Mitigate CVE-2026-40865

Immediate Actions Required

• Review and audit all document access endpoints for proper authorization controls
• Implement server-side validation to verify the authenticated user owns or has explicit access rights to requested documents
• Consider temporarily restricting document viewer access to administrators until proper controls are implemented
• Conduct a forensic review of document access logs to identify potential exploitation

Patch Information

Users should monitor the GitHub Security Advisory for official patch information and updates from the Horilla maintainers. Upgrade to the latest patched version as soon as one becomes available.

Workarounds

• Implement network-level access restrictions to limit HRMS access to trusted networks or VPN users only
• Add additional authentication layers or step-up authentication for accessing sensitive document functionality
• Implement server-side access control checks in the document viewer endpoint to validate document ownership
• Use unpredictable document identifiers (UUIDs) instead of sequential integers to reduce enumeration risk
• Deploy a web application firewall with rules to detect and block IDOR exploitation patterns