CVE-2025-27915 — Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
2025-10-07 • CISA Known Exploited Vulnerability
[event] Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.
> AFFECTED SOFTWARE
| Field | Value |
|---|---|
| Vendor | Synacor |
| Product | Zimbra Collaboration Suite (ZCS) |
| CWE | CWE-79 |
| CVE ID | CVE-2025-27915 |
| Date Added | 2025-10-07 |
| Due Date | 2025-10-28 |
| Ransomware Campaign | Unknown |
> MITIGATION
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Due Date: 2025-10-28