Actively exploited · Published Mar 12, 2025 · Assigned by mitre

CVE-2025-27915

Medium 5.4 Exploited

In plain English

A medium-severity cross-site scripting in Zimbra Collaboration Suite (ZCS) from Synacor. Attackers are actively exploiting it in the wild (listed by CISA on October 7, 2025). The chance it is exploited in the next 30 days is estimated at 4.1% (higher than 91% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Severity (CVSS 3.1)5.4Medium

Exploit odds (30 days)4.1%top 9.3% of all CVEs

Exploited in the wildYesCISA KEV since Oct 7, 2025

Attack tooling1Nuclei

CISA guidance

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Federal agencies must remediate by Oct 28, 2025.

Official 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.

Affected products (as reported)

Vendor	Product	Versions
n/a	n/a	n/a

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

In plain English

CISA guidance

Official description

Affected products (as reported)

References