CVE-2019-9621 Synacor Zimbra Collaboration Suite (ZCS): web page flaw
In plain words: A web app can be made to act on someone's behalf or reach places it should not. Stolen sessions, actions taken as the victim, or access to internal systems.
Confirmed exploited by CISA on · US federal patch deadline Jul 28, 2025
What to do
- Install Synacor's security update for Zimbra Collaboration Suite (ZCS). If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Keep a list of every internet-facing server you run so nothing is forgotten.
- Patch anything in this catalog first, ahead of normal patch cycles.
- Put admin and file-transfer apps behind a VPN or single sign-on instead of the open internet.
Who is affected
Work IT. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.
What's at risk: Mass data theft and ransomware: a single flaw in a file-transfer or email server has exposed thousands of organisations at once.
The details
- Official name
- Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery (SSRF) Vulnerability
- Product
- Synacor Zimbra Collaboration Suite (ZCS)
- CISA description
- Synacor Zimbra Collaboration Suite (ZCS) contains a server-side request forgery (SSRF) vulnerability via the ProxyServlet component.
- Type of flaw
- Web page flaw (CWE-918, CWE-807)
- Confirmed exploited
- Jul 7, 2025
- US federal patch deadline
- Jul 28, 2025
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Answering about CVE-2019-9621 ·
Questions about CVE-2019-9621
Is CVE-2019-9621 being exploited?
Yes. CISA added CVE-2019-9621 to its Known Exploited Vulnerabilities catalog on Jul 7, 2025, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2019-9621?
Install Synacor's security update for Zimbra Collaboration Suite (ZCS). If no update exists, follow the vendor's workaround or stop using the product until one ships. Keep a list of every internet-facing server you run so nothing is forgotten.
Am I affected by CVE-2019-9621?
Only if you use Synacor Zimbra Collaboration Suite (ZCS). Aimed mostly at company systems — you are affected through the companies you use, not your own phone.