CVE-2026-66912: medium-severity vulnerability in Synacor Zimbra Collaboration
Stored Cross-Site Scripting in Zimbra
Published · Updated
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.3epss 0.5%
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
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Affected products
Synacor · Zimbra CollaborationRelated CVEs — Synacor Zimbra Collaboration
In the same product, most dangerous first.