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Nearly 22,000 Microsoft Exchange servers remain exposed to critical security flaw (CVE-2026-62911)

About 22,000 Microsoft Exchange servers remain unpatched against critical auth bypass CVE-2026-62911 as a working exploit circulates online.

CVE-2026-62911 is a critical authentication bypass by capture-replay in Microsoft Exchange Server that allows an authorized attacker to elevate privileges over the network, with a CVSS score of 8.0. Microsoft patched the flaw on August 11, 2026, but Shadowserver Foundation scans show roughly 22,000 servers unpatched, with the US (6,200) and Germany (5,100) leading; BSI reports 85% of on-premises Exchange servers in Germany are still vulnerable. The Netherlands' NCSC-NL flagged that a working exploit is circulating, and Exchange 2016/2019 require the Extended Security Updates program for fixes.

Help Net Security · 13d agoExploit / PoC in the wildCVE-2026-62911CVE-2026-42897