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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-93647
StatePUBLISHED
Assignerrapid7
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-25 14:17:23 UTC
Updated2026-09-28 13:17:25 UTC
DescriptionAn 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.

Risk And Classification

Primary CVSS: v3.1 9.3 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

EPSS: 0.002290000 probability, percentile 0.123530000 (date 2026-09-27)

Problem Types: CWE-79 | CWE-79 CWE-79 Improper neutralization of input during web page generation ('cross-site scripting')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.3CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
3.1CNACVSS9.3CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Zimbra Zimbra Collaboration Suite ZCS affected 10.1.21 semver Not specified

References

ReferenceSourceLinkTags
wiki.zimbra.com/wiki/Zimbra_Security_Advisories [email protected] wiki.zimbra.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Jonah Burgess (CryptoCat), Senior Security Researcher, Rapid7 (en)

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report