# CVE-2024-27443: Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability

> CVE-2024-27443: Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability. CVSS 6.1 (CVSS 3.1), in CISA KEV.

Canonical: https://rewindex.com/cve/CVE-2024-27443
Last updated: 2025-10-21T22:55:48Z

- Published: 2024-08-12 00:00 UTC · Updated: 2025-10-21 22:55 UTC · Assigner: mitre
- CVSS: 6.1 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- EPSS: 24.6%, 98th percentile (scored 2026-10-25)
- CISA KEV: yes, added 2025-05-19, federal due date 2025-06-09, ransomware use: Unknown

## Description

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.

## CISA required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

## Affected vendors and products

- Synacor: Zimbra Collaboration Suite (ZCS)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2024-27443)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2024-27443)
- [https://wiki.zimbra.com/wiki/Zimbra\_Releases/10.0.7\#Security\_Fixes](https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes)
- [https://wiki.zimbra.com/wiki/Zimbra\_Releases/9.0.0/P39\#Security\_Fixes](https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_Fixes)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2024-27443 · Markdown: https://rewindex.com/cve/CVE-2024-27443.md · JSON: https://rewindex.com/api/v1/cves/CVE-2024-27443 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:11:20.299Z