CVE-2021-34807: Zimbra Collaboration

Medium severity, CVSS 6.1. EPSS: 1% chance of exploitation in the next 30 days.

An open redirect vulnerability exists in the /preauth Servlet in Zimbra Collaboration Suite through 9.0. To exploit the vulnerability, an attacker would need to have obtained a valid zimbra auth token or a valid preauth token. Once the token is obtained, an attacker could redirect a user to any URL via isredirect=1&redirectURL= in conjunction with the token data (e.g., a valid authtoken= value).

Affected products

• Zimbra Collaboration: before 8.8.15 (fixed in 8.8.15); version 8.8.15 only; version 9.0.0 only

Published 2021-07-02. Last modified 2026-06-17.