CVE-2019-9621
Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery (SSRF) Vulnerability
Synacor Zimbra Collaboration Suite (ZCS)
Zimbra Collaboration Suite before 8.6 patch 13, 8.7.x before 8.7.11 patch 10, and 8.8.x before 8.8.10 patch 7 or 8.8.x before 8.8.11 patch 3 allows SSRF via the ProxyServlet component.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 7 July 2025. US federal agencies were required to remediate it by 28 July 2025.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 81%, which is higher than 99.6% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Frequently asked questions
Is CVE-2019-9621 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2019-9621.
What does CVE-2019-9621 affect?
CVE-2019-9621 affects Synacor Zimbra Collaboration Suite (ZCS). Zimbra Collaboration Suite before 8.6 patch 13, 8.7.x before 8.7.11 patch 10, and 8.8.x before 8.8.10 patch 7 or 8.8.x before 8.8.11 patch 3 allows SSRF via the ProxyServlet component.
How severe is CVE-2019-9621?
CVE-2019-9621 is rated HIGH with a CVSS base score of 7.5. EPSS puts the probability of exploitation in the next 30 days at 81%, higher than 99.6% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 28 July 2025.
How should organisations respond to CVE-2019-9621?
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.