MailEnable Enterprise Premium versions prior to 10.62 contain a heap overflow in the IMAP X-FB-FETCH command. The implementation of the optional X-FB-USER field formats the supplied address without a length check, allowing an authenticated user to provide a value longer than 1016 bytes that overflows a fixed 0x400‑byte heap buffer. When triggered, the resulting memory corruption causes the IMAP service to crash, resulting in a denial of service for all clients that rely on that service. The vulnerability only requires that the attacker has valid IMAP authentication credentials; no privilege escalation or code execution is achieved.

MailEnable Enterprise Premium systems running any version prior to 10.62 are vulnerable. This includes all installations that have not applied an update to version 10.62 or later.

The CVSS score of 7.1 (Medium‑High) reflects the service‑crash impact and the requirement for authentication to exploit the flaw. EPSS data is not available, meaning historical exploit data is unknown. The vulnerability is not listed in the CISA KEV catalog, so no publicly known exploitation campaigns are reported. Attackers would need to authenticate to the IMAP service, which is typically limited to legitimate users, but once authenticated they could send the specially crafted X-FB-USER command to crash the server. The lack of a readily available public exploit tool raises the technical barrier, but the impact on availability makes it a high‑priority concern.