Answer in brief
CVE-2026-66911 records a Medium severity (CVSS 5.3) vulnerability in Stored Cross-Site Scripting in Zimbra. The current sources do not mark it as known exploited. The current feed maps Synacor/Zimbra Collaboration (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Synacor/Zimbra Collaboration (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Synacor/Zimbra Collaborationgeneric | >=0 <10.1.21 | 10.1.21 |
Published upstream
Oct 29, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 29, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Oct 29, 2026
Zimbra is vulnerable to stored cross-site scripting (XSS) via the Content-Location MIME header in email attachments. Due to lack of sanitization of the Content-Location header, an attacker can set it to a javascript: URI. An unauthenticated remote attacker can send a crafted email to a victim; when the victim opens the email in the Zimbra web interface and clicks the attachment name, the JavaScript payload executes in the victim's browser context. This issue was fixed in version 10.1.21
Quoted source text, attributed separately from HOL analysis.