CVE-2026-48189: OTRS Information Disclosure Vulnerability

CVE-2026-48189 Overview

CVE-2026-48189 is an improper input validation vulnerability in the OTRS Customer Backend module. The flaw allows an authenticated user to access customer information that should be restricted to other groups. Exploitation requires the affected feature to be enabled and CustomerGroupSupport to be in use. The vulnerability is categorized under [CWE-200] Information Exposure and affects multiple OTRS release lines from version 7.0.X through 2026.X prior to 2026.4.X.

Critical Impact

Authenticated attackers can read customer records belonging to groups they are not authorized to access, breaking the tenant isolation provided by CustomerGroupSupport.

Affected Products

• OTRS 7.0.X and 8.0.X
• OTRS 2023.X, 2024.X, and 2025.X
• OTRS 2026.X before 2026.4.X

Discovery Timeline

• 2026-06-01 - CVE-2026-48189 published to NVD
• 2026-06-01 - Last updated in NVD database

Technical Details for CVE-2026-48189

Vulnerability Analysis

The OTRS Customer Backend module enforces group-based access control through the CustomerGroupSupport feature. This feature segments customer records so that agents only retrieve data tied to groups they belong to. CVE-2026-48189 breaks that boundary by failing to validate input passed to the customer lookup logic. An authenticated user can craft a request that bypasses the group check and returns customer information owned by groups outside their permission set. The issue requires user interaction and low privileges, and the impact is limited to confidentiality. No integrity or availability impact has been reported by the vendor.

Root Cause

The root cause is improper input validation [CWE-200] inside the Customer Backend module. The module accepts user-supplied parameters that influence which customer records are returned without enforcing the group restriction defined by CustomerGroupSupport. Because the authorization check is incomplete, the backend processes the request and returns records from groups that the requester should not see.

Attack Vector

The vulnerability is exploitable over the network by an authenticated low-privilege user. The attacker submits a request to the Customer Backend that references customer data outside their assigned groups. User interaction is required, which typically means a victim agent must trigger an action that loads attacker-influenced parameters. No verified proof-of-concept code has been published. See the OTRS Security Advisory 2026-03 for the vendor's technical description.

Detection Methods for CVE-2026-48189

Indicators of Compromise

• Customer Backend queries returning records associated with groups the requesting agent does not belong to.
• Spikes in customer search or lookup activity from accounts that historically interact with a narrow group scope.
• Audit log entries showing access to CustomerID values outside an agent's assigned CustomerGroup mapping.

Detection Strategies

• Compare each agent's group membership against the CustomerID values returned in their Customer Backend responses and alert on mismatches.
• Enable verbose logging on the Customer Backend module and correlate request parameters with the authorizing user's group list.
• Review web server access logs for unusual query strings targeting customer lookup endpoints from low-privilege accounts.

Monitoring Recommendations

• Forward OTRS application and web logs to a centralized analytics platform and retain them long enough to support retroactive review.
• Build a baseline of normal customer record access volumes per agent and alert on deviations.
• Monitor for repeated lookup attempts that iterate across CustomerID ranges, which can indicate enumeration.

How to Mitigate CVE-2026-48189

Immediate Actions Required

• Upgrade OTRS to release 2026.4.X or later, which contains the vendor fix.
• Inventory all OTRS instances and confirm whether CustomerGroupSupport is enabled, since only those deployments are exposed.
• Review recent Customer Backend access logs for evidence of cross-group customer data retrieval.
• Rotate credentials for any agent account suspected of having been used to access unauthorized customer data.

Patch Information

OTRS has released fixed builds in the 2026.4.X line. Customers on 7.0.X, 8.0.X, 2023.X, 2024.X, 2025.X, or earlier 2026.X versions must upgrade to a remediated release. Refer to the OTRS Security Advisory 2026-03 for vendor-supplied upgrade guidance and release notes.

Workarounds

• If immediate patching is not feasible, disable the affected Customer Backend feature until the upgrade can be applied.
• Temporarily disable CustomerGroupSupport-dependent workflows and restrict customer data access to administrator accounts.
• Restrict network access to the OTRS web interface to trusted management networks to reduce the pool of users who can authenticate.