CVE-2025-27915
Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
This vulnerability is in the CISA Known Exploited Vulnerabilities catalog: attackers are using it. If you run Zimbra Collaboration Suite (ZCS), fix it now.
CISA 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.
US federal civilian agencies must remediate by Oct 28, 2025.
Patch status
No official fix confirmed yet
Until a fix ships, follow the vendor's mitigations and CISA's required action, limit exposure of affected systems, and watch this record for a patch.
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.
Source: NIST National Vulnerability Database. Official vulnerability data, reproduced as published.
Affected products
| Product | Vendor | Affected versions | Fixed in | Source |
|---|---|---|---|---|
| Zimbra Collaboration Suite | Synacor | >= 10.0.0, < 10.0.13; >= 10.1.0, < 10.1.5; 9.0.0 | 10.0.13; 10.1.5 | NVD |
| Zimbra Collaboration Suite (ZCS) | Synacor | — | — | KEV |
Sources: NVD = NIST National Vulnerability Database; KEV = CISA Known Exploited Vulnerabilities catalog.
Intelligence timeline
Developments from the last 30 days, newest first.
- CVSS scoredUpdateKEV
CVE-2025-27915 scored CVSS 5.4: Synacor Zimbra Collaboration Suite (ZCS), Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
CISA lists this as exploited in the wild. Unpatched Zimbra Collaboration Suite (ZCS) systems are exposed to active attacks now.
Basis: NIST National Vulnerability Database
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Coverage
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