CVE-2026-35023 Overview
CVE-2026-35023 is an Insecure Direct Object Reference (IDOR) vulnerability affecting Wimi Teamwork On-Premises versions prior to 8.2.0. The vulnerability exists in the preview.php endpoint where the item_id parameter lacks proper authorization checks. Attackers with valid credentials can enumerate sequential item_id values to access and retrieve image previews from other users' private or group conversations, resulting in unauthorized disclosure of sensitive information.
Critical Impact
Authenticated attackers can bypass authorization controls to access private image content belonging to other users, potentially exposing confidential business communications and sensitive visual data shared within private conversations.
Affected Products
- Wimi Teamwork On-Premises versions prior to 8.2.0
Discovery Timeline
- 2026-04-08 - CVE-2026-35023 published to NVD
- 2026-04-09 - Last updated in NVD database
Technical Details for CVE-2026-35023
Vulnerability Analysis
This vulnerability is classified as CWE-639 (Authorization Bypass Through User-Controlled Key), commonly known as an Insecure Direct Object Reference (IDOR). The preview.php endpoint in Wimi Teamwork On-Premises accepts an item_id parameter that directly references image preview resources stored on the server. The fundamental security flaw lies in the absence of proper authorization validation—the application verifies that a user is authenticated but fails to confirm whether that user is authorized to access the specific resource identified by the item_id.
The vulnerability is exploitable over the network by any authenticated user. The attack requires low complexity and no user interaction, making it straightforward to exploit once an attacker has valid credentials on the system. The primary impact is on confidentiality, as attackers can view image previews from conversations they should not have access to.
Root Cause
The root cause is improper access control implementation in the preview.php endpoint. The application relies solely on authentication state rather than implementing proper authorization checks to verify that the requesting user has legitimate access to the specific item_id being requested. This architectural weakness allows any authenticated user to access any image preview by simply knowing or guessing the corresponding item_id value.
Attack Vector
The attack vector operates through the network via authenticated HTTP requests to the preview.php endpoint. An attacker with valid user credentials can perform the following exploitation technique:
- Authenticate to the Wimi Teamwork On-Premises application with valid credentials
- Identify the preview.php endpoint that serves image previews
- Enumerate item_id parameter values sequentially (e.g., item_id=1, item_id=2, etc.)
- Access image previews belonging to other users' private or group conversations
- Harvest sensitive visual content from conversations the attacker is not authorized to view
The sequential nature of item_id values makes enumeration trivial—attackers can automate requests to systematically retrieve large volumes of image previews across the entire application.
Detection Methods for CVE-2026-35023
Indicators of Compromise
- Unusual volume of requests to preview.php from a single authenticated user
- Sequential or patterned item_id parameter values in rapid succession from the same session
- Access patterns showing a user retrieving image previews from conversations they are not members of
- Anomalous spikes in image preview access compared to baseline user behavior
Detection Strategies
- Implement web application firewall (WAF) rules to detect and alert on rapid sequential parameter enumeration
- Configure application logging to capture all preview.php access requests with user context and item_id values
- Deploy anomaly detection to identify users accessing abnormally high volumes of image previews
- Cross-reference access logs to identify users retrieving content from conversations where they have no membership
Monitoring Recommendations
- Enable detailed access logging for the preview.php endpoint including timestamps, user IDs, and requested item_id values
- Set up alerting thresholds for request rates to preview.php that exceed normal usage patterns
- Monitor for authentication events followed by bulk enumeration activity
- Review access logs periodically for evidence of parameter tampering or brute-force enumeration attempts
How to Mitigate CVE-2026-35023
Immediate Actions Required
- Upgrade Wimi Teamwork On-Premises to version 8.2.0 or later immediately
- Conduct an audit of preview.php access logs to identify potential exploitation attempts
- Review any accounts showing anomalous image preview access patterns for signs of compromise
- Consider temporarily restricting access to the preview.php endpoint while planning the upgrade
Patch Information
The vulnerability has been addressed in Wimi Teamwork On-Premises version 8.2.0. Organizations should upgrade to this version or later to remediate the IDOR vulnerability. Detailed update information is available from the Wimi Teamwork Product Update page. Additional technical details can be found in the VulnCheck Security Advisory.
Workarounds
- Implement a web application firewall (WAF) rule to rate-limit requests to preview.php per authenticated session
- Add network-level access controls to restrict preview.php access to trusted internal networks if external access is not required
- Monitor and alert on suspicious access patterns while awaiting the upgrade deployment
- Consider implementing custom authorization middleware at the web server level to validate user access rights before forwarding requests to preview.php
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
