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CVE-2026-66912 Details

Description

Zimbra is vulnerable to Stored Cross-Site Scripting (XSS) via the From email header during HTML reply composition in Classic UI. Due to insufficient sanitization of the From header value, a remote attacker can send a crafted email containing a malicious From header with an embedded JavaScript payload. When the victim opens the message in Classic UI and clicks Reply while composing in HTML mode with reply headers disabled, the unsanitized From header content is rendered as HTML and the JavaScript payload executes in the victim's browser, potentially allowing the attacker to steal session information or perform actions on behalf of the victim. This issue was fixed in version 10.1.21

Metrics

CVSS 3.x Severity and Vector Strings:

No CVSS 3.x data is available for this CVE.

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://cert.pl/en/posts/2026/10/CVE-2026-66911	[email protected]
https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories	[email protected]

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-79	Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')	[email protected]

Affected Products

No affected product data is available for this CVE.

Change History

2 change records found show changes

Date	Action	Recorded By
Nov 5, 2026	CVE Modified	CISA-ADP
Oct 29, 2026	New CVE Received	[email protected]