CVE-2026-33371

low-risk

Published 2026-03-20

An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. An XML External Entity (XXE) vulnerability exists in the Zimbra Exchange Web Services (EWS) SOAP interface due to improper handling of XML input. An authenticated attacker can submit crafted XML data that is processed by an XML parser with external entity resolution enabled. Successful exploitation may allow disclosure of sensitive local files from the server.

Do I need to act?

0.05% chance of exploitation

EPSS score — low exploit probability

Not on CISA KEV list

No confirmed active exploitation reported to CISA

Patch status unknown

Check vendor advisories for fix availability and mitigation guidance

CVSS 4.3/10 Medium

NETWORK / LOW complexity

Affected Products (1)

Zimbra Collaboration Suite

Affected Vendors

Synacor

References (4)

Vendor Advisory https://wiki.zimbra.com/wiki/Security_Center

Release Notes https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.16#Security_Fixes

Product https://wiki.zimbra.com/wiki/Zimbra_Responsible_Disclosure_Policy

Vendor Advisory https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories

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low-risk

Severity 18/34 · Moderate

Exploitability 0/34 · Minimal

Exposure 5/34 · Minimal