CVE-2021-35208

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-07-02 · updated 2026-06-17
Weakness: CWE-79

Description

An issue was discovered in ZmMailMsgView.js in the Calendar Invite component in Zimbra Collaboration Suite 8.8.x before 8.8.15 Patch 23. An attacker could place HTML containing executable JavaScript inside element attributes. This markup becomes unescaped, causing arbitrary markup to be injected into the document.

Affected products

Zimbra Collaboration: from 8.8 before 8.8.15; 8.8.15, 8.8.15-p1, 8.8.15-p10, 8.8.15-p11, 8.8.15-p12, 8.8.15-p13 (+17) — fixed in 8.8.15

How to fix

Upgrade to a fixed version: Zimbra Collaboration 8.8.15. Check the vendor advisory for mitigations.

References

https://blog.sonarsource.com/zimbra-webmail-compromise-via-email
https://wiki.zimbra.com/wiki/Security_Center
https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P23
https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P16
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
https://blog.sonarsource.com/zimbra-webmail-compromise-via-email
https://wiki.zimbra.com/wiki/Security_Center
https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P23
https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P16
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories

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