---
id: "CVE-2024-27443"
kind: "vulnerability"
aliases: ["CVE-2024-27443"]
title: "An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0"
severity: "high"
cvss: 6.1
epss: null
exploited: true
status: "open"
category: "package"
products: [{"name": "Synacor Zimbra Collaboration Suite (ZCS)", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "zimbra collaboration", "fixed": ["10.0.7"], "affected": ">= 10.0.0, < 10.0.7", "ecosystem": "vendor"}, {"name": "zimbra collaboration", "fixed": [], "affected": "= 9.0.0", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["email", "exploited", "package", "self-hosted", "zimbra"]
not_affected_if: ["zimbra-modern-ui-only"]
published_at: "2024-08-12T15:15:20+00:00"
first_seen_at: "2026-10-23T19:11:51+00:00"
updated_at: "2026-10-23T22:29:05+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2024-27443", "first_seen_at": "2026-10-23T19:11:51+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-27443", "first_seen_at": "2026-10-23T22:29:05+00:00"}]
---

# An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0

Zimbra Collaboration Suite's classic webmail interface has a cross-site scripting flaw in its CalendarInvite feature. A crafted calendar header in an email runs attacker-chosen JavaScript in the victim's browser session.

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

## Affected

- vendor:Synacor Zimbra Collaboration Suite (ZCS) affected ? fixed ?
- vendor:zimbra collaboration affected >= 10.0.0, < 10.0.7 fixed 10.0.7
- vendor:zimbra collaboration affected = 9.0.0 fixed ?

## Fix

Apply the vendor mitigations per CISA guidance (vendor instructions not in sources); or discontinue use of the product if mitigations are unavailable.

## Timeline

- 2026-10-23T19:11:51+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2024-27443
- 2026-10-23T22:29:05+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2024-27443

## From the sources

An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0. A Cross-Site Scripting (XSS) vulnerability exists in the CalendarInvite feature of the Zimbra webmail classic user interface, because of improper input validation in the handling of the calendar header. An attacker can exploit this via an email message containing a crafted calendar header with an embedded XSS payload. When a victim views this message in the Zimbra webmail classic interface, the payload is executed in the context of the victim's session, potentially leading to execution of arbitrary JavaScript code.

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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_