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CVE-2025-27915

MEDIUM severity · CVSS 5.4 · Cross-site scripting (XSS) · actively exploited (CISA KEV)
5.4CVSS MEDIUM exploited
Actively exploited in the wild (CISA Known Exploited Vulnerabilities). Added to KEV 2025-10-07. US federal agencies must patch by 2025-10-28.

Summary

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.

Impact & exploitability

Attack vectorNetwork
Attack complexityLow
Privileges requiredLow
User interactionRequired
Confidentiality impactLow
Integrity impactLow
Availability impactNone
Exploit probability (EPSS)4%

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

Affected products we track (1)

Zimbra Collaboration Suite (ZCS)

Recommendation

This vulnerability is being actively exploited in the wild — patch affected products urgently. Open any affected product above for its exact safe version.

Additional information