CVE-2019-9621: Synacor Zimbra Collaboration Suite SSRF in ProxyServlet

CVE-2019-9621 · Severity: critical · CVSS 7.5 · Exploited in the wild · Published 2025-07-07

Zimbra Collaboration Suite, a widely used enterprise email and collaboration platform, contains a security flaw in its proxy component. An attacker can exploit this to force the server to make unauthorized requests to internal or external systems, potentially leading to the exposure of sensitive internal data. This vulnerability has been observed being used in active attacks.

Technologies: Synacor Zimbra Collaboration Suite (ZCS). Vendors: Synacor.

Quick answers

Is CVE-2019-9621 exploited in the wild?
Yes. CVE-2019-9621 is known to be exploited in the wild, first recorded on 7 July 2025. Treat it as urgent.
How severe is CVE-2019-9621?
Critical severity, with a CVSS score of 7.5, published 7 July 2025.
Which products and versions are affected?
Synacor Zimbra Collaboration Suite Before 8.6 Patch 13, 8.7.x before 8.7.11 Patch 10, 8.8.x before 8.8.10 Patch 7, and 8.8.x before 8.8.11 Patch 3.
Is there a fix for CVE-2019-9621?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2019-9621 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2019-9621?
Check whether you run Synacor Zimbra Collaboration Suite (ZCS). Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A Server-Side Request Forgery (SSRF) vulnerability exists in the ProxyServlet component of Synacor Zimbra Collaboration Suite (ZCS). The flaw allows a remote, unauthenticated attacker to send specially crafted requests that the server will then forward to other internal or external services. This can be used to bypass network segmentation, access internal-only metadata services, or facilitate further attacks such as remote code execution when combined with other vulnerabilities. The issue is resolved in 8.6 Patch 13, 8.7.11 Patch 10, 8.8.10 Patch 7, and 8.8.11 Patch 3.

Affected products

  • Synacor Zimbra Collaboration Suite Before 8.6 Patch 13, 8.7.x before 8.7.11 Patch 10, 8.8.x before 8.8.10 Patch 7, and 8.8.x before 8.8.11 Patch 3

Timeline

  • 2019-03-01: advisory: Initial vendor advisory published
  • 2025-07-07: kev added: Added to CISA Known Exploited Vulnerabilities catalog

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