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CVE-2026-55007: Microsoft Exchange Server Remote Code Execution Vulnerability

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-08 · updated 2026-10-31
• Weakness: CWE-415

Description

Double free in Microsoft Exchange Server allows an unauthorized attacker to execute code over a network.

Affected products

• Microsoft Exchange Server: 2019-cumulative_update_14, 2019-cumulative_update_15
• Microsoft Exchange Server Subscription Edition: before 15.02.2562.049 — fixed in 15.02.2562.049
• Microsoft Exchange Server 2019 Cumulative Update 14: from 15.02.0.0 before 15.02.1544.046 — fixed in 15.02.1544.046
• Microsoft Exchange Server 2019 Cumulative Update 15: from 15.02.0.0 before 15.02.1748.051 — fixed in 15.02.1748.051
• Microsoft Exchange Server Subscription Edition RTM: from 15.02.0.0 before 15.02.2562.049 — fixed in 15.02.2562.049

How to fix

Upgrade to a fixed version: Microsoft Exchange Server Subscription Edition 15.02.2562.049; Microsoft Exchange Server 2019 Cumulative Update 14 15.02.1544.046; Microsoft Exchange Server 2019 Cumulative Update 15 15.02.1748.051; Microsoft Exchange Server Subscription Edition RTM 15.02.2562.049. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55007

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