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TI-2026-39716 Aliases CVE-2026-55009GHSA-78c8-h6hm-94hg

Microsoft Exchange Server Elevation of Privilege Vulnerability

Priority MEDIUM 41CWE-502Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Privilege escalation
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Microsoft. Impact type from Microsoft.

Summary

Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.02513 84th percentileScored 2026-11-07
Fix Fixed Microsoft: 4 updates

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MicrosoftMicrosoft Exchange Server 2016 Cumulative Update 2315.01.0.0 to before 15.01.2507.07115.01.2507.071Patch availableCNA
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 1415.02.0.0 to before 15.02.1544.04315.02.1544.043Patch availableCNA
MicrosoftMicrosoft Exchange Server 2019 Cumulative Update 1515.02.0.0 to before 15.02.1748.04815.02.1748.048Patch availableCNA
MicrosoftMicrosoft Exchange Server Subscription Edition RTM15.02.0.0 to before 15.02.2562.04515.02.2562.045Patch availableCNA
  • Microsoft Exchange Server 2016 Cumulative Update 23 VendorMicrosoft Affected 15.01.0.0 to before 15.01.2507.071 Fixed in 15.01.2507.071 Patch available CNA
  • Microsoft Exchange Server 2019 Cumulative Update 14 VendorMicrosoft Affected 15.02.0.0 to before 15.02.1544.043 Fixed in 15.02.1544.043 Patch available CNA
  • Microsoft Exchange Server 2019 Cumulative Update 15 VendorMicrosoft Affected 15.02.0.0 to before 15.02.1748.048 Fixed in 15.02.1748.048 Patch available CNA
  • Microsoft Exchange Server Subscription Edition RTM VendorMicrosoft Affected 15.02.0.0 to before 15.02.2562.045 Fixed in 15.02.2562.045 Patch available CNA

CPE configurations NVD · 4

CPEVersionsRoleVendor
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_23:*:*:*:*:*:*2016 cumulative_update_23VulnerableMicrosoft
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_14:*:*:*:*:*:*2019 cumulative_update_14VulnerableMicrosoft
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_15:*:*:*:*:*:*2019 cumulative_update_15VulnerableMicrosoft
cpe:2.3:a:microsoft:exchange_server_subscription_edition:*:*:*:*:*:*:*:*before 15.02.2562.045VulnerableMicrosoft
  • cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_23:*:*:*:*:*:* Versions 2016 cumulative_update_23 Vulnerable ·Microsoft
  • cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_14:*:*:*:*:*:* Versions 2019 cumulative_update_14 Vulnerable ·Microsoft
  • cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_15:*:*:*:*:*:* Versions 2019 cumulative_update_15 Vulnerable ·Microsoft
  • cpe:2.3:a:microsoft:exchange_server_subscription_edition:*:*:*:*:*:*:*:* Versions before 15.02.2562.045 Vulnerable ·Microsoft

Remediation

Microsoft 4 updates

  • KB5103215
    Security Update
    • Microsoft Exchange Server 2016 Cumulative Update 23 15.01.2507.071
  • KB5103214
    Security Update
    • Microsoft Exchange Server 2019 Cumulative Update 14 15.02.1544.043
  • KB5103213
    Security Update
    • Microsoft Exchange Server 2019 Cumulative Update 15 15.02.1748.048
Show 1 more Microsoft updates
  • KB5103212
    Security Update
    • Microsoft Exchange Server Subscription Edition RTM 15.02.2562.045

Vendor assessments

Microsoft

Microsoft's page for this CVE →

Impact
Elevation of Privilege
Exploited
No
Publicly disclosed
No
Exploitability
Exploitation Unlikely

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-55009
  2. 2026-10-03 Alias added: GHSA-78c8-h6hm-94hg

References

Patch 1

  • TI-2024-14170 Microsoft Exchange Server Elevation of Privilege Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2022-19610 Microsoft Exchange Server Elevation of Privilege Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2021-13547 Microsoft Exchange Server Elevation of Privilege Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2021-13502 Microsoft Exchange Server Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2021-08465 Microsoft Exchange Server Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8
  • TI-2023-07929 Microsoft Exchange Server Remote Code Execution Vulnerability KEVCVSS 3.1HIGH 8.8
See all 258 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences