---
id: "CVE-2026-93636"
kind: "vulnerability"
aliases: ["CVE-2026-93636"]
title: "Zimbra: authenticated users can read hidden calendar resource attributes via LDAP injection"
severity: "medium"
cvss: 4.3
epss: 0.00306
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["email", "ldap", "package", "self-hosted", "zimbra"]
not_affected_if: ["no-zimbra", "unaffected-version"]
published_at: "2026-10-23T14:17:57+00:00"
first_seen_at: "2026-10-23T21:57:34+00:00"
updated_at: "2026-10-25T12:38:49+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93636", "first_seen_at": "2026-10-23T21:57:34+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-93636", "first_seen_at": "2026-10-25T12:38:49+00:00"}]
---

# Zimbra: authenticated users can read hidden calendar resource attributes via LDAP injection

An authenticated Zimbra Collaboration Suite user can inject LDAP filter conditions through the attribute names in SearchCalendarResourcesRequest. Repeated matching queries let them recover readable calendar resource attributes such as internal mailbox hostnames and mail transport routes.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed ZCS version with `su - zimbra -c "zmcontrol -v"`; versions 10.1.16 and 10.1.21 are affected.
- unknown for other checks; the sources do not describe log or configuration indicators.

## Fix

- Upgrade Zimbra Collaboration Suite to a release that includes the fix for this issue; the sources do not name the fixed version.
- unknown for a workaround; the sources do not give one.

## Timeline

- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-93636
- 2026-10-25T12:38:49+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-93636

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_