CVE-2025-27915

synacor zimbra collaboration suite

Published 12 Mar 2025 · updated 17 Jun 2026 · Analyzed

5.4 Medium · CVSS 3.1, CISA ADP

Exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on 7 Oct 2025, with a remediation deadline of 28 Oct 2025 for US federal agencies.

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.

References