CVE-2026-34248: Zammad Information Disclosure Vulnerability

CVE-2026-34248 Overview

Zammad is a web-based open source helpdesk and customer support system. A vulnerability exists in versions prior to 7.0.1 that allows customers in shared organizations to view ticket fields that are not intended for customer access. When a customer opens a ticket created by another user within the same shared organization, they can see internal-only fields such as priority values and custom ticket attributes designated for internal purposes. While the exposed fields are read-only and cannot be modified by unauthorized customers, this information disclosure could reveal sensitive operational data.

Critical Impact

Customers in shared organizations can view internal ticket fields (priority, custom attributes) from other users' tickets, potentially exposing sensitive operational information not intended for customer visibility.

Affected Products

• Zammad versions prior to 7.0.1
• Zammad installations with shared organization feature enabled
• Self-hosted and cloud deployments using shared organization configurations

Discovery Timeline

• 2026-04-08 - CVE CVE-2026-34248 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2026-34248

Vulnerability Analysis

This vulnerability represents a Broken Access Control (CWE-284) issue within Zammad's shared organization feature. The shared organization functionality is designed to allow customers within the same organization to view each other's tickets for collaboration purposes. However, the implementation fails to properly filter field visibility based on the viewing customer's access level.

When a customer accesses a ticket belonging to another user in their shared organization, the application returns all ticket fields in the response without applying customer-specific field visibility rules. This means fields configured as "internal only" or restricted to specific user roles are inadvertently exposed to all customers within the shared organization context.

The vulnerability requires specific conditions to exploit: the attacker must be an authenticated customer belonging to a shared organization, and there must be other tickets from different users within that same organization. The information exposed is limited to read access—no modification capabilities are granted.

Root Cause

The root cause stems from insufficient access control validation in the ticket field rendering logic when tickets are accessed through the shared organization view. The application correctly restricts direct ticket access but fails to apply the same field-level visibility rules when serving ticket data in the shared organization context. The field filtering mechanism that normally hides internal fields from customers is bypassed during cross-user ticket viewing within shared organizations.

Attack Vector

The attack vector is network-based and requires authenticated access with low attack complexity. An attacker would need valid customer credentials and membership in a shared organization to exploit this vulnerability.

The exploitation flow involves:

1. Authenticating as a customer belonging to a shared organization
2. Navigating to view tickets created by other users within the same organization
3. Observing ticket fields that should be hidden from customer view, including priority fields and custom internal attributes

Since this is an information disclosure vulnerability requiring user interaction and specific organizational configurations, the practical exploitation requires the attacker to already have legitimate access to the Zammad instance as a customer with shared organization membership.

Detection Methods for CVE-2026-34248

Indicators of Compromise

• Unusual access patterns to tickets across multiple users within shared organizations
• Customers accessing ticket detail views for tickets they did not create
• API responses containing internal field data when accessed by customer-level users

Detection Strategies

• Review access logs for customers viewing tickets outside their direct ownership
• Monitor API endpoints serving ticket data for responses containing internal field names
• Audit shared organization configurations to identify potentially affected deployments

Monitoring Recommendations

• Enable detailed logging for ticket access within shared organizations
• Implement alerts for high-volume cross-user ticket viewing activities
• Periodically review which fields are marked as internal and verify they are not exposed in customer-facing views

How to Mitigate CVE-2026-34248

Immediate Actions Required

• Upgrade Zammad to version 7.0.1 or later immediately
• Review shared organization configurations and assess exposure risk
• Audit internal ticket fields that may have been exposed to customers
• Consider temporarily disabling shared organization features until patching is complete

Patch Information

The vulnerability is fixed in Zammad version 7.0.1. Organizations should upgrade to this version or later to remediate the information disclosure issue. For additional details on the security fix, refer to the GitHub Security Advisory.

Workarounds

• Disable the shared organization feature if not critical to operations until the patch can be applied
• Review and minimize internal-only custom fields to reduce exposure risk
• Implement network-level access controls to limit who can access the Zammad instance
• Consider temporarily separating sensitive tickets into non-shared organizations

# Example: Check current Zammad version
zammad version

# Upgrade Zammad to patched version (method depends on installation type)
# For package-based installations:
apt-get update && apt-get upgrade zammad

# Verify upgrade was successful
zammad version
# Expected output: 7.0.1 or higher