CVE-2025-27915

medium

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.

https://www.cisa.gov/news-events/alerts/2025/10/07/cisa-adds-one-known-exploited-vulnerability-catalog

https://securityaffairs.com/183085/hacking/u-s-cisa-adds-synacor-zimbra-collaboration-suite-zcs-flaw-to-its-known-exploited-vulnerabilities-catalog.html

https://www.darkreading.com/cyberattacks-data-breaches/attackers-exploit-zimbra-zero-day-ics

https://securityaffairs.com/183014/hacking/zimbra-users-targeted-in-zero-day-exploit-using-icalendar-attachments.html

https://www.bleepingcomputer.com/news/security/hackers-exploited-zimbra-flaw-as-zero-day-using-icalendar-files/

https://thehackernews.com/2025/10/zimbra-zero-day-exploited-to-target.html

https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes

https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_Fixes

https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_Fixes

https://wiki.zimbra.com/wiki/Security_Center

Details

Source: Mitre, NVD

Published: 2025-03-12

Updated: 2025-10-08

Known Exploited Vulnerability (KEV)

Risk Information

CVSS v2

Base Score: 5.5

Vector: CVSS2#AV:N/AC:L/Au:S/C:P/I:P/A:N

Severity: Medium

CVSS v3

Base Score: 5.4

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

Severity: Medium

EPSS

EPSS: 0.30233

Vulnerability Watch

Tenable Research has classified this CVE under the following Vulnerability Watch classification, which includes active and historical (inactive) classifications. You can learn more about these classifications on our blog.

Vulnerability of Interest

Detections

Analytics