CVE-2025-27915 — Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
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 maliciou
Published
2025-03-12T00:00:00.000Z
Last modified
2026-02-26T19:09:35.780Z
CISA KEV — Actively Exploited
01What is this vulnerability?
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…
02Affected products
| Vendor | Product | Versions |
|---|
| n | a / n/a | n/a |
03Active exploitation status
Yes — actively exploited. Added to the CISA KEV catalog on 2025-10-07. Ransomware use: Unknown.
04Recommended remediation
- Patch to a fixed version listed in the vendor advisory (see references below).
- Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
- Hunt historical logs for exploitation indicators — see Detection signatures below.
05Technical details
For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.
06Detection signatures
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07Related CVEs
No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.
08Timeline
- Published: 2025-03-12T00:00:00.000Z
- Last modified: 2026-02-26T19:09:35.780Z
- Added to CISA KEV: 2025-10-07
- BOD 22-01 due: 2025-10-28
09References
- wiki.zimbra.com — https://wiki.zimbra.com/wiki/Security_Center
- wiki.zimbra.com — https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_Fixes
- wiki.zimbra.com — https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_Fixes
- wiki.zimbra.com — https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes
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