CISA KEV catalog
Confirmed active exploitation.
Listed in CISA's catalog of Known Exploited Vulnerabilities: attackers are using it in real attacks. Patch it with priority.
- Name
- Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability
- Added to catalog
- Remediation due date (US federal)
- 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.
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.
Affected products
zimbra: collaboration
References4
- wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes Release Notes
- wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_Fixes Release Notes
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=… US Government Resource
- www.welivesecurity.com/en/eset-research/operation-roundpress/ Press/Media Coverage
Metrics
- CVSS 3.1
-
6.1
MEDIUM
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - EPSS — exploit probability
- 25% percentile: 98 · as of 3 November 2026
- CWE
- CWE-79
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