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CVE-2024-27443

Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS)

6.1 MEDIUMActively exploited (CISA KEV)EPSS 23.6%
  1. Published12 Aug 2024
  2. Added to CISA KEV19 May 2025
  3. Remediation due9 Jun 2025
Actively exploited (CISA KEV)

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.

Added to KEV: 19 May 2025Federal remediation due: 9 Jun 2025

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionRequired
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected products

Zimbra Collaboration≥ 10.0.0 < 10.0.7 · 9.0.0

Remediation

Fixed in
Zimbra Collaboration≥ 10.0.7

References

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Frequently asked

Is CVE-2024-27443 being actively exploited?

Yes. CVE-2024-27443 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 19 May 2025.

How severe is CVE-2024-27443?

CVE-2024-27443 has a CVSS 3.1 base score of 6.1, rated medium. EPSS estimates a 23.6% probability of exploitation.

Which products are affected by CVE-2024-27443?

Affected products include Zimbra Collaboration.

How do I fix CVE-2024-27443?

Upgrade affected software to a fixed version, for example Zimbra Collaboration 10.0.7 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2024-27443 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.