Assessment
Why it matters
CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 3.9%; technical severity is CVSS 5.4.
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.
Who should care
- Teams operating Zimbra Collaboration Suite, Zimbra Collaboration Suite (ZCS)
- Vulnerability and exposure management teams
- Security operations teams monitoring exploitation activity
Response plan
What I would do
- Confirm whether Zimbra Collaboration Suite, Zimbra Collaboration Suite (ZCS) is present in the environment.
- Identify affected versions and establish whether vulnerable services are exposed or reachable.
- Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- Review relevant security telemetry for evidence of attempted or successful exploitation.
- Document the remediation decision and track it to verified completion.
Treatment intelligence
Remediation intelligence
Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.
Upgrade
- Wiki Zimbra Security release notes Security CenterWiki ZimbraVerification pending ↗
- Wiki Zimbra Security release notes 10.0.13Wiki ZimbraVerification pending ↗
- Wiki Zimbra Security release notes 10.1.5Wiki ZimbraVerification pending ↗
- Wiki Zimbra Security release notesWiki ZimbraVerification pending ↗
Technical details
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
- CWE
- CWE-79
- Affected versions
- Synacor Zimbra Collaboration Suite (Start Including 10.0.0, End Excluding 10.0.13 | Start Including 10.1.0, End Excluding 10.1.5 | Version 9.0.0 | Version 9.0.0); Synacor Zimbra Collaboration Suite (ZCS)
- Fixed versions
- Synacor Zimbra Collaboration Suite (Fixed from 10.0.13, 10.1.5)
- Published
- 12 March 2025
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- Required
Signal timeline
- CVE published
- Added to CISA KEV
- Latest EPSS score: 3.9%
- Signal calculated at 64