CVE-2026-44400 is an improper authorization vulnerability (CWE-639) affecting MailEnable Enterprise Premium 10.55 and earlier. The vulnerability exists in the WebAdmin mobile portal where AuthenticationToken cookies generated for low-privileged users can be reused to bypass authentication. Attackers can exploit this by obtaining a token from the WebMail login endpoint with the PersistentLogin parameter and replaying it against the WebAdmin portal, enabling unauthorized administrative access. The CVSS 4.0 base score is 8.7, indicating high severity with network attack vector, low attack complexity, no user interaction, and high impact on confidentiality, integrity, and availability.

Successful exploitation allows attackers to bypass authentication and perform highly privileged administrative actions on the MailEnable Enterprise Premium WebAdmin portal. This can lead to full administrative control over the affected system, compromising confidentiality, integrity, and availability of the mail server environment.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is currently documented. Until a patch is available, restrict access to the WebAdmin portal and monitor for suspicious authentication token reuse if possible.