CVE-2025-27915
MediumExploitedPublic exploitA stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files.
Published Mar 12, 2025 · Updated Sep 14, 2026
Key Facts
Patch immediately- CVE-2025-27915 is a medium-severity vulnerability (CVSS 5.4 v3.1) affecting Zimbra Collaboration Suite (Synacor).
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Sep 30, 2025. Public exploit code is available.
- EPSS estimates a 4.1% probability of exploitation in the next 30 days.
- Fixed versions are available, including Zimbra Collaboration Suite 10.0.13.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
5.4
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
EPSS (30-day exploit likelihood)
4.1%
Higher than 90.5% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2025-27915 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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 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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Oct 7, 2025 | Oct 28, 2025 | Not reported |
| Industry KEV feed | Sep 30, 2025 | Oct 28, 2025 | Not reported |
| CIRCL KEV | Oct 7, 2025 | Oct 28, 2025 | Not reported |
| ENISA EUVD | Oct 7, 2025 | n/a | Not reported |
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.
Affected Products
46 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Zimbra Collaboration SuiteSynacor | 9.0.0, 9.0.0-p1, 9.0.0-p10, 9.0.0-p11, 9.0.0-p12, 9.0.0-p13, 9.0.0-p14, 9.0.0-p15 | 10.0.13 |
Patched Releases
Zimbra Collaboration Suite
10.0.13
Timeline
Publicly disclosed
Mar 12, 2025
Added to Industry KEV feed
Sep 30, 2025
Added to CISA KEV
Oct 7, 2025
Added to CIRCL KEV
Oct 7, 2025
Added to ENISA EUVD
Oct 7, 2025
Last updated
Sep 14, 2026
Weakness Type
- CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
References
- advisoryhttps://github.com/CVEProject/cvelistV5/tree/main/cves/2025/27xxx/CVE-2025-27915.json
- advisoryhttps://nvd.nist.gov/vuln/detail/CVE-2025-27915
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
- exploitVulnCheck exploitation report
FAQ
Common Questions.
An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1.
Affected: Zimbra Collaboration Suite (Synacor) versions 9.0.0, 9.0.0-p1, 9.0.0-p10, 9.0.0-p11, 9.0.0-p12, 9.0.0-p13, 9.0.0-p14, 9.0.0-p15. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Sep 30, 2025.
Yes. It was added on Oct 7, 2025 with a federal remediation due date of Oct 28, 2025.
Public exploit code is available.
Fixed versions are available, including Zimbra Collaboration Suite 10.0.13.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
Is CVE-2025-27915 Running On Your Attack Surface?
Brandefense maps vulnerabilities like this one to your internet-facing assets and tells you exactly where to patch.
Request A Demo