CVE-2026-73570 Synacor Zimbra Collaboration Suite (ZCS): command or code injection
In plain words: The program treats text it receives as instructions instead of plain data. The attacker can run commands on the machine — often the whole device is taken over.
Confirmed exploited by CISA on · US federal patch deadline Aug 24, 2026
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
- Zimbra Collaboration Suite (ZCS) OS Command Injection Vulnerability
- Product
- Synacor Zimbra Collaboration Suite (ZCS)
- CISA description
- Zimbra Collaboration Suite (ZCS) contains an OS command injection vulnerability which could allow an unauthenticated attacker to send specially crafted SMTP requests that may result in execution of arbitrary operating system commands as the Zimbra user.
- Type of flaw
- Command or code injection (CWE-78)
- Confirmed exploited
- Aug 21, 2026
- US federal patch deadline
- Aug 24, 2026
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Answering about CVE-2026-73570 ·
Questions about CVE-2026-73570
Is CVE-2026-73570 being exploited?
Yes. CISA added CVE-2026-73570 to its Known Exploited Vulnerabilities catalog on Aug 21, 2026, which means there is reliable evidence of real-world attacks.
How do I fix CVE-2026-73570?
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-2026-73570?
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.