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

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.

VendorSynacor
ProductZimbra Collaboration Suite (ZCS)
Date added to KEV2025-05-19
Due date (BOD 22-01)2025-06-09
Known ransomware campaign useUnknown
CWECWE-79
Required actionApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

What to do

  1. Identify every instance of Synacor Zimbra Collaboration Suite (ZCS) in your environment (asset inventory, EDR, vulnerability scanner).
  2. Apply CISA's 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.
  3. Federal civilian agencies must act by 2025-06-09 under BOD 22-01; other organizations can use the same date as a target.
  4. Check the vendor advisory and NVD entry linked below for affected versions, then record the fix in your change log.

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Sources

Generated from the CISA feed with AI assistance; facts are taken verbatim from the feed. Not affiliated with or endorsed by CISA. Facts come from the CISA Known Exploited Vulnerabilities catalog (public domain).