Vulnerability 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
Related Weaknesses (CWE)
References
- https://cert.pl/en/posts/2026/10/CVE-2026-66911
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
FAQ
What is CVE-2026-66912?
CVE-2026-66912 is a documented vulnerability. 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 att...
How severe is CVE-2026-66912?
CVSS scoring is not yet available for CVE-2026-66912. Check NVD for updates.
Is there a patch for CVE-2026-66912?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.