Nearly 22,000 Microsoft Exchange servers vulnerable to hijack attacks

Nearly 22,000 Microsoft Exchange servers remain exposed and unpatched against a high-severity authentication bypass vulnerability. This vulnerability enables attackers to hijack all user mailboxes on affected servers. The report does not specify which versions are affected or if a patch is available. No known active exploitation has been reported. The vulnerability is significant due to the potential for complete mailbox compromise.

Successful exploitation of this vulnerability allows attackers to bypass authentication controls and gain full access to all user mailboxes on the affected Microsoft Exchange servers. This could lead to unauthorized data access, data theft, and potential further compromise of the affected organization’s email infrastructure.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Organizations should verify their Microsoft Exchange servers are up to date with the latest security patches from Microsoft. Until patches are applied, restricting external access to Exchange servers and monitoring for suspicious activity is advisable.