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Synacor, Zimbra Collaboration Suite (ZCS)
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.
CVSS severity
Medium (6.1/10)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Sourced from NVD, reflects how severe this vulnerability is if exploited, not whether it has been. Every advisory on this page is already a CISA-confirmed active exploitation case regardless of its CVSS score.
EPSS, exploit probability
High24.6%
estimated chance of real-world exploitation in the next 30 days, higher than 97.9% of every CVE FIRST.org scores
Refreshed 10/28/2026, via FIRST.org's EPSS model, not CVSS, this measures likelihood of exploitation, not how severe it would be.
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.
CISA-recommended due date: 2025-06-09
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