Actively exploited · Published Jan 5, 2026 · Assigned by mitre
CVE-2025-66376
High 7.2 Exploited
In plain English
A high-severity cross-site scripting in Collaboration from Zimbra. Attackers are actively exploiting it in the wild (listed by CISA on March 18, 2026). The chance it is exploited in the next 30 days is estimated at 20.2% (higher than 97% of all known vulnerabilities). Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
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 Apr 1, 2026.
Official description
Zimbra Collaboration (ZCS) 10 before 10.0.18 and 10.1 before 10.1.13 allows Classic UI stored XSS via Cascading Style Sheets (CSS) @import directives in an HTML e-mail message.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Zimbra | Collaboration | 10.0 – before 10.0.1810.1 – before 10.1.13 |
Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
References
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
- https://wiki.zimbra.com/wiki/Security_Center
- https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.13#Security_Fixes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.18#Security_Fixes
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-66376 government-resource