CVE-2025-27915: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
In CISA’s Known Exploited Vulnerabilities catalog: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability.
Added , federal remediation due . Known ransomware use: Unknown.
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Description
An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability 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 <details> 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.
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Status incidents that name it
No tracked status incident names this CVE.
Affected vendors and products
Synacor: Zimbra Collaboration Suite (ZCS)
References
- CVE record on cve.org (opens in new tab)
- NVD entry (opens in new tab)
- wiki.zimbra.com/wiki/Security_Center (opens in new tab)
- wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13 (opens in new tab)
- wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5 (opens in new tab)
- wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44 (opens in new tab)
- CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (opens in new tab)
- This product uses data from the NVD API but is not endorsed or certified by the NVD. (opens in new tab)
- Known Exploited Vulnerabilities catalog from CISA. (opens in new tab)
- EPSS scores from FIRST (Exploit Prediction Scoring System). (opens in new tab)