Microsoft Exchange Server 2016 Cumulative Update 23 vulnerabilities

6 CVEs affecting Microsoft Exchange Server 2016 Cumulative Update 23, 0 known to be exploited (CISA KEV), with EPSS scores. Latest: CVE-2026-87696, published 2026-10-13.

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Known exploited (CISA KEV) first, then by EPSS exploit probability.

• CVE-2026-87692, published 2026-10-13. High severity, CVSS 7.8. EPSS: 1.6% chance of exploitation in the next 30 days. Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
• CVE-2026-70571, published 2026-10-13. High severity, CVSS 8.1. EPSS: 0.9% chance of exploitation in the next 30 days. Stack-based buffer overflow in Microsoft Exchange Server allows an unauthorized attacker to execute code over a network.
• CVE-2026-70279, published 2026-10-13. Critical severity, CVSS 9.3. EPSS: 0.9% chance of exploitation in the next 30 days. Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.
• CVE-2026-77910, published 2026-10-13. High severity, CVSS 8.8. EPSS: 0.8% chance of exploitation in the next 30 days. Incorrect authorization in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.
• CVE-2026-87696, published 2026-10-13. High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days. Improper verification of cryptographic signature in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.
• CVE-2026-87695, published 2026-10-13. High severity, CVSS 7.8. EPSS: 0.2% chance of exploitation in the next 30 days. Inclusion of functionality from untrusted control sphere in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.