CVE-2026-93636: Zimbra Collaboration Suite LDAP Filter Injection via Calendar Resource Attribute Name
An LDAP filter injection vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to query otherwise unreturned attributes of calendar resources through SearchCalendarResourcesRequest. Zimbra escapes search values but inserts the supplied attribute names directly into LDAP filter expressions without validation. An attacker can inject additional conditions and use repeated matching queries to recover readable resource attributes such as internal mailbox hostnames and mail transport routes. The search remains restricted to calendar-resource objects and the LDAP service account's access rights. ZCS 10.1.16 and 10.1.21 are affected.
Affected Software
Event History
Frequently Asked Questions
Who can exploit this issue?
An attacker must be authenticated to Zimbra Collaboration Suite and able to send SearchCalendarResourcesRequest queries. Exploitation is limited to calendar-resource objects and to attributes readable by the LDAP service account.
What information could be exposed?
The issue can expose otherwise unreturned readable attributes of calendar resources. Examples identified include internal mailbox hostnames and mail transport routes; confidentiality impact is rated low, with no integrity or availability impact stated.
Are default deployments affected?
The affected versions identified are ZCS 10.1.16 and 10.1.21. The provided information does not state whether a particular non-default configuration is required beyond authenticated access and calendar-resource searching.
How can an organization determine whether it may be affected?
Review whether any Zimbra Collaboration Suite deployments run version 10.1.16 or 10.1.21. Investigate authenticated SearchCalendarResourcesRequest activity for unusual or repeated queries, which may indicate attempts to infer resource attributes through injected LDAP filter conditions.