CVE-2025-48700
Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
Synacor Zimbra Collaboration Suite (ZCS)
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 20 April 2026. US federal agencies were required to remediate it by 23 April 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 1.8%, which is higher than 75.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
Frequently asked questions
Is CVE-2025-48700 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2025-48700.
What does CVE-2025-48700 affect?
CVE-2025-48700 affects Synacor Zimbra Collaboration Suite (ZCS).
How severe is CVE-2025-48700?
EPSS puts the probability of exploitation in the next 30 days at 1.8%, higher than 75.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 23 April 2026.
How should organisations respond to CVE-2025-48700?
Apply the vendor patch for Synacor Zimbra Collaboration Suite (ZCS) as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.