CISA KEV entry
CVE-2025-27915Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
Synacor Zimbra Collaboration Suite (ZCS). Added to the CISA Known Exploited Vulnerabilities catalogue on 7 October 2025.
Data status: a source is stale
Last synced CISA catalogue version 2026.11.04 (released 4 November 2026) 1,768 entries Updated manually
- Date added
- 2025-10-07
- Federal due date
- 2025-10-28 21 days after it was added; passed at the sync of 2026-11-05
- Known ransomware use
- Unknown
- Forensic triage (BOD 26-04)
- No
- CVSS
- 5.4 Medium CVSS 3.1, scored by CISA ADP
- EPSS
- 4.06% percentile 90.6, scored 2026-11-04
- CISA SSVC
- Exploitation active, automatable no, technical impact total
- NVD status
- Analyzed published 2025-03-12, 209 days before the KEV listing
BOD 26-04 remediation window
With CISA's SSVC answers for this CVE (automatable: no, technical impact: total), BOD 26-04 Table 1 gives 3 days and forensic triage on a publicly exposed asset (row 3) and 14 days on an asset that is not publicly exposed (row 11) S06. The catalogue due date, 21 days after the date added, was set before BOD 26-04 took effect on 10 June 2026 S06. The directive binds US federal civilian executive branch agencies only.
What CISA says
Short description
Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that 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.
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.
Notes
https://wiki.zimbra.com/wiki/Security_Center ; https://nvd.nist.gov/vuln/detail/CVE-2025-27915
CWE in the catalogue
CWE-79
Official links
- CISA KEV catalogue entry cisa.gov
- NVD record nvd.nist.gov
Vendor advisory and patch links
No vendor advisory linked by NVD.
Links in CISA's notes
NVD details
- CWE (NVD)
- CWE-79 by CISA ADP
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N- CVSS versions in NVD
- V31
- Last modified in NVD
- 2026-06-17T09:04:22.957
Where each value comes from
| Field | Source | Fetched, UTC | State |
|---|---|---|---|
| Catalogue fields | CISA KEV JSON, version 2026.11.04 | 2026-11-05 11:38 | current |
| NVD published, status, CVSS, CWE, vendor links | NVD CVE API 2.0; CVSS: NVD (CISA ADP) | 2026-11-03 12:37 | current at 2026-11-05 11:38 |
| EPSS | FIRST EPSS API, scores of 2026-11-04 | 2026-11-05 11:38 | current |
| CISA SSVC | CISA ADP (via NVD), record of 2025-10-07 | 2026-11-03 12:37 | current |
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