IRONSMITHINTEL
HIGHCVSS7.5
|
Actively Exploited
|CISA KEV|CVE-2019-9621|Auth: none — unauthenticated|Reboot: required|Manual only

Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery (SSRF) Vulnerability

Synacor Zimbra Collaboration Suite (ZCS) contains a server-side request forgery (SSRF) vulnerability via the ProxyServlet component.

Published Apr 30, 2019 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve full data confidentiality loss. Federal agencies are required to remediate by 2025-07-28 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Server-Side Request Forgery (SSRF) (CWE-918) vulnerability in 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 requires remote network access, low attack complexity, no authentication required, and no user interaction required.

📧

Phishing link

→

🖼

Malicious file

🔓

Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

●IT Security
●Running zimbra collaboration suite: v < 8.6.0, 8.7.0 ≤ v < 8.7.11, 8.8.0 ≤ v < 8.8.9, 8.6.0, 8.7.11, 8.8.9, 8.8.10, 8.8.11
Real-world incidentsWhat we've seen

Active exploitation documented in the wild. Threat-research write-up: http://packetstormsecurity.com/files/152487/Zimbra-Collaboration-Autodiscover-Servlet-XXE-ProxyServlet-SSRF.html

How to patch

Manual remediation steps

Apply the Vendor Patch

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.

CISA 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.

References

    1
    Vendor advisory: https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2019-9621
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2019-9621
PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ CVE-2019-9621↗ NVD↗ Vendor Advisory