CVE-2025-27915
Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
Exploited in the wild
This vulnerability is on the CISA Known Exploited Vulnerabilities list, added 2025-10-07. Federal due date: 2025-10-28.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Impact
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 products
| Vendor | Product | Affected versions |
|---|---|---|
| Synacor | Zimbra Collaboration Suite | from 10.0.0 before 10.0.13 from 10.1.0 before 10.1.5 Version 9.0.0 |
Weakness classification
References
- NVD record
- CVE.org record
- CISA KEV catalog
- https://wiki.zimbra.com/wiki/Security_Center
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_Fixes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_Fixes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes
- https://strikeready.com/blog/0day-ics-attack-in-the-wild/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-27915