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Nearly 22,000 Microsoft Exchange servers vulnerable to hijack attacks
September 1, 2026 · BleepingComputer · Severity: HIGH
Nearly 22,000 Microsoft Exchange servers exposed online remain unpatched against a high-severity authentication bypass vulnerability that allows attackers to hijack all user mailboxes.
Key Takeaways
- Nearly 22,000 Microsoft Exchange servers are unpatched against a critical authentication bypass flaw.
- Attackers can hijack all user mailboxes on vulnerable Exchange servers remotely.
- Organizations must urgently patch their Exchange servers to prevent mailbox takeover attacks.