CVE-2025-66376
Exploitation confirmed. First attested on 2026-03-18 by CISA-ADP, CISA KEV, GCVE · kevintel.
- Published2026-01-05
- Fixed in10.1.13 · 10.0.18
- WeaknessCWE-79
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « affected ».With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.
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.
Timeline
dates in UTCObserved activity
isMalicious corpus · updated 2026-10-23 18:48 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2025-66376?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2025-66376?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 10.1 | ≥ 10.1.0, < 10.1.13 | 10.1.13 | NVD |
| 10.0 | ≥ 10.0.0, < 10.0.18 | 10.0.18 | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Fix
- Update Synacor zimbra collaboration suite to 10.1.13 · 10.0.18
- CISA’s 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.due 2026-04-01
Advisories and patches
- wiki.zimbra.comRelease Notes · Vendor Advisory
- wiki.zimbra.comRelease Notes
- wiki.zimbra.comRelease Notes
- wiki.zimbra.comVendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
CISA Known Exploited Vulnerability
- Date Added
- 2026-03-18
- Patch Due Date
- 2026-04-01
- Ransomware Use
- Unknown
- 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.
Sources
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- Published
- 2026-01-05
- Last Modified
- 2026-10-07
- NVD status
- Analyzed
Frequently asked questions
What is CVE-2025-66376?
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What is the CVSS score for CVE-2025-66376?
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Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.