Exploited CVEs / Synacor / CVE-2024-27443
CVE-2024-27443
Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted. Federal agencies were required to remediate by 2025-06-09 (that deadline has passed); treat that date as the outer bound for your own environment. The fix is in the vendor advisory: Zimbra Security Center, linked below.
Actively exploited Synacor Zimbra Collaboration Suite (ZCS) vulnerability, Medium severity, CVSS 6.1. Added to the CISA KEV catalog 2025-05-19.
Risk summary
Updated July 30, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Senserva AI Opinion for CVE-2024-27443
Despite its Medium Severity rating at CVSS 6.1, this Zimbra Collaboration XSS made the CISA KEV list on 2025-05-19 because attackers are actively exploiting it: a crafted calendar header in an email executes script in the classic webmail interface when the victim opens the message. Mail-borne XSS in webmail platforms is a staple of credential and mailbox theft, and Zimbra has been a repeat target. Organizations still on the classic UI are the exposed population.
Do this: Patch Zimbra Collaboration and move users off the classic webmail interface where possible.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2024-27443
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2024-27443
Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.
CISA required action
Federal (BOD 22-01) remediation due date: 2025-06-09 (past due).
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Official fix for CVE-2024-27443
The authoritative fix and affected-version list are published by the vendor. Find the Zimbra Collaboration Suite (ZCS) advisory on Zimbra Security Center.
Common questions about CVE-2024-27443
Is CVE-2024-27443 actively exploited?
Yes. CVE-2024-27443 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2025-05-19, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 24%.
What is the CISA deadline and required action for CVE-2024-27443?
CISA set the federal (BOD 22-01) remediation due date at 2025-06-09, which has passed; treat any unremediated system as overdue. The verbatim 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.
What fixes CVE-2024-27443?
The authoritative fix is in the vendor advisory: see Zimbra Security Center for the patched Zimbra Collaboration Suite (ZCS) versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.
Can I ask my own AI about CVE-2024-27443?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2024-27443's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).
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Authoritative references
Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.
