CVE-2026-93647 Zimbra Classic - Stored XSS

Zimbra Classic contains a stored XSS caused by active markup in a COUNTER message's RFC From address, letting unauthenticated calendar senders access mailbox data and act as victims, exploit requires message selection.

CVSS base score 9.3 /10
Critical
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.23% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Stored XSS
Impact
Stored XSS, Information Disclosure
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Published
25 September 2026
Updated
15 October 2026
Weakness
CWE-79

Vendor fix

Update to the latest version with XSS protections.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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