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CVE-2026-70279: Microsoft Exchange Server Spoofing Vulnerability

• Severity: critical (CVSS 9.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-13 · updated 2026-10-31
• Weakness: CWE-79

Description

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.

Affected products

• Microsoft Exchange Server 2016 Cumulative Update 23: from 15.01.0.0 before 15.01.2507.077 — fixed in 15.01.2507.077
• Microsoft Exchange Server 2019 Cumulative Update 14: from 15.02.0.0 before 15.02.1544.050 — fixed in 15.02.1544.050
• Microsoft Exchange Server 2019 Cumulative Update 15: from 15.02.0.0 before 15.02.1748.055 — fixed in 15.02.1748.055
• Microsoft Exchange Server Subscription Edition RTM: from 15.02.0.0 before 15.02.2562.056 — fixed in 15.02.2562.056

How to fix

Upgrade to a fixed version: Microsoft Exchange Server 2016 Cumulative Update 23 15.01.2507.077; Microsoft Exchange Server 2019 Cumulative Update 14 15.02.1544.050; Microsoft Exchange Server 2019 Cumulative Update 15 15.02.1748.055; Microsoft Exchange Server Subscription Edition RTM 15.02.2562.056. Check the vendor advisory for mitigations.

In the news

• Microsoft’s October 2026 Patch Tuesday addresses 1407 CVEs (CVE-2026-96951)

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70279

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