CVE-2026-50055: CWE-863 Incorrect Authorization in Zimbra Zimbra Collaboration Suite

This vulnerability (CVE-2026-50055) in Zimbra Collaboration Suite involves a policy enforcement weakness (CWE-863) where an authenticated user can circumvent disabled mail forwarding restrictions. The bypass is performed by leveraging the Sieve notify action, which can send copies of email content and headers to an arbitrary external address despite forwarding being disabled. The issue affects versions before 10.1.20. The CVSS 3.1 base score is 6.5, indicating a medium severity with network attack vector, low attack complexity, and requiring low privileges with no user interaction. Confidentiality impact is high, while integrity and availability impacts are none.

An authenticated user can bypass mail forwarding restrictions and exfiltrate email content and headers to arbitrary addresses. This could lead to unauthorized disclosure of sensitive email information. The vulnerability does not affect integrity or availability of the system. There are no known active exploits in the wild.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no patch or official fix information is provided, users should monitor vendor communications for updates. In the meantime, restricting user permissions and reviewing Sieve script usage may help reduce risk.