Zimbra Classic XSS via COUNTER Message From header
CVE-2026-93647 Published on September 25, 2026
Zimbra Collaboration Suite Classic Web Client Stored Cross-Site Scripting via Crafted Calendar COUNTER Message From Address
An unauthenticated calendar sender can place active markup in a COUNTER message's RFC From address. Selecting the message in Zimbra Classic triggers stored XSS, allowing the attacker to access mailbox data and act as the victim.
Vulnerability Analysis
CVE-2026-93647 can be exploited with network access, requires user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.
Weakness Type
What is a XSS Vulnerability?
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
CVE-2026-93647 has been classified to as a XSS vulnerability or weakness.
Products Associated with CVE-2026-93647
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Affected Versions
Zimbra Collaboration Suite (ZCS):- Before 10.1.21 is affected.