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

criticalknown exploitedpublic exploitCVE-2024-27443
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation as urgent.
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.

CSIRTS triage

vendor: Zimbraproduct: Zimbra Collaboration SuiteCross-site scripting
What
There is a cross-site scripting (XSS) vulnerability in the CalendarInvite feature of the Zimbra webmail classic user interface.
Who is affected
Deployments of Zimbra Collaboration Suite that utilize the affected feature.
Urgency
Remediation is urgent due to active exploitation and critical severity.
Action
Apply the latest security patch provided by Zimbra.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
CISA Known Exploited Vulnerabilities (US · database · site)
Severity
critical
Published
2025-05-19
Exploitation
Observed in the wild (CISA KEV)

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2024-27443

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2024-27443coverage & exploitation statusNVD · CVE.org

Recent advisories for Synacor Zimbra Collaboration

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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