# CVE-2025-27915: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability

> CVE-2025-27915: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability. CVSS 5.4 (CVSS 3.1), in CISA KEV.

Canonical: https://rewindex.com/cve/CVE-2025-27915
Last updated: 2026-06-17T09:04:22Z

- Published: 2025-03-12 00:00 UTC · Updated: 2026-06-17 09:04 UTC · Assigner: mitre
- CVSS: 5.4 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
- EPSS: 4.1%, 91th percentile (scored 2026-10-25)
- CISA KEV: yes, added 2025-10-07, federal due date 2025-10-28, ransomware use: Unknown

## 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.

## 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.

## Affected vendors and products

- Synacor: Zimbra Collaboration Suite (ZCS)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2025-27915)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2025-27915)
- [https://wiki.zimbra.com/wiki/Security\_Center](https://wiki.zimbra.com/wiki/Security_Center)
- [https://wiki.zimbra.com/wiki/Zimbra\_Releases/10.0.13\#Security\_Fixes](https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_Fixes)
- [https://wiki.zimbra.com/wiki/Zimbra\_Releases/10.1.5\#Security\_Fixes](https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_Fixes)
- [https://wiki.zimbra.com/wiki/Zimbra\_Releases/9.0.0/P44\#Security\_Fixes](https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2025-27915 · Markdown: https://rewindex.com/cve/CVE-2025-27915.md · JSON: https://rewindex.com/api/v1/cves/CVE-2025-27915 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:12:49.147Z