Medium 6.1Known exploited (CISA KEV)Published Aug 12, 2024

CVE-2024-27443An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0.

Updated under an hour ago (2026-10-19 06:25 UTC)

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It affects zimbra collaboration. Add what you run to find out whether that includes you.

CISA lists it as known exploited since May 19, 2025; federal agencies had to remediate by Jun 9, 2025. Treat that date as your deadline.

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Exploited in the last 30 days

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.

CVSS: 6.1 MEDIUM (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness (CWE): CWE-79
Known exploited: Added to CISA KEV May 19, 2025; federal remediation due Jun 9, 2025Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
EPSS (exploitation in the next 30 days): 24.61% (percentile 98)
Assigned by: mitre
NVD analysis: Analyzed
Record last updated: Oct 21, 2025
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

zimbra collaboration zimbra:collaboration	from 10.0.0 before 10.0.7; 9.0.0; 9.0.0; 9.0.0; 9.0.0; 9.0.0; 9.0.0; 9.0.0; and 30 more ranges	NVD

References

https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixesrelease-notes
https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_Fixesrelease-notes
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-27443us-government-resource
https://www.welivesecurity.com/en/eset-research/operation-roundpress/press/media-coverage

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.