May 19, 2025 · Applied Cybernetics Group
CVE-2024-27443 — Synacor Zimbra Collaboration Suite (ZCS)
Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability
- Added to KEV
2025-05-19- Federal due date
2025-06-09- Vendor
- Synacor
- Product
- Zimbra Collaboration Suite (ZCS)
- EPSS
- 97.1th percentile (score 0.195, as of
2026-07-13) - NVD CVSS v3.1
- —
- Ransomware use
- Unknown
- ATT&CK
- T1041 , T1059.004 , T1114 , T1566.002 · signal rollup
- Upstream
- https://nvd.nist.gov/vuln/detail/CVE-2024-27443
CISA short description
Zimbra Collaboration contains a cross-site scripting (XSS) vulnerability in the CalendarInvite feature of the Zimbra webmail classic user interface. An attacker can exploit this vulnerability via an email message containing a crafted calendar header, leading to the execution of arbitrary JavaScript code.
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.