Zimbra Collaboration Suite Email HTML Sanitizer Bypass via Hostname Canonicalization
A hostname canonicalization vulnerability in the email HTML sanitizers of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to bypass the restriction on forms that target the Zimbra host. DefangFilter and the OWASP ActionAttributePolicy compare the form-action hostname with the request hostname before browser URL canonicalization. A percent-encoded hostname can therefore survive sanitization while the browser submits the form to the normal Zimbra origin with the recipient's authentication cookie. This permits authenticated form requests from a crafted email after the recipient opens it in Classic and submits the form. The issue is present in ZCS 10.1.16 and 10.1.21. It does not bypass an endpoint's CSRF-token checks; a state-changing attack additionally requires an endpoint that accepts the resulting request without that protection.
CVE-2026-93630
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-93630
Zimbra Collaboration Suite
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "Zimbra",
"product": "Zimbra Collaboration Suite",
"versions": [
{
"status": "affected",
"version": "0",
"lessThan": "10.1.21",
"versionType": "semver"
}
],
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-93630
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #52922 · Revision 1
- Added to Heist Feed
- Publisher date