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CRITICAL

CVE-2026-93647

Zimbra Collaboration Suite Classic Web Client Stored Cross-Site Scripting via Crafted Calendar COUNTER Message From Address

CVSS v3

9.3

CRITICAL

EPSS Score

0.2 %

exploit probability, as of 2026-09-29

CISA KEV

No

known exploited

Exploitation

—

SSVC status

Description

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.

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Published
2026-09-25
Last Modified
2026-09-26

Frequently asked questions

What is CVE-2026-93647?

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.

Is CVE-2026-93647 actively exploited?

Active exploitation of CVE-2026-93647 has not been confirmed. Its EPSS score was 0.2% on 2026-09-29, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-93647?

CVE-2026-93647 has a CVSS v3 base score of 9.3 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N.

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