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Microsoft Security Response CenterCVE-2026-69378

Microsoft Exchange Server Denial of Service Vulnerability

Uncontrolled recursion in Microsoft Exchange Server allows an unauthorized attacker to deny service over a network.

Read the vendor bulletin Get alerts for Microsoft Exchange Server 2016 Cumulative Update
7.5CVSS out of 10High severity
Scope

What the vendor says is affected

  • Microsoft Exchange Server 2016 Cumulative Update 23
  • Microsoft Exchange Server 2019 Cumulative Update 14
  • Microsoft Exchange Server Subscription Edition RTM
  • Microsoft Exchange Server 2019 Cumulative Update 15

Versions the vendor lists as fixed

  • 15.01.2507.073
  • 15.02.1544.046
  • 15.02.2562.049
  • 15.02.1748.051
Next step

What the vendor recommends

Install KB5121611. Install KB5121610. Install KB5121608. Install KB5121609.

Review the complete instructions on the vendor's site
Timeline

When this advisory changed

  1. Published by Microsoft Security Response Center

    The publication date reported by the vendor.

  2. Added to SecurityAlert

    We collected the advisory from the official source.

  3. Confirmed at the source

    Our collector saw this advisory during a later source check.

Vulnerabilities

CVEs named in this advisory

CVE-2026-69378View CVSS, KEV, EPSS, and threat context
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