CVE-2025-53786Network attack vector

Cloud privilege escalation via shared service-principal trust

Published Aug 6, 2025 · Updated Feb 26, 2026

Improper authentication in Microsoft Exchange Server hybrid deployments allows remote authenticated users to control connected Exchange Online. The Hybrid Configuration Wizard uploads the on-premises Auth Certificate to a shared first-party service principal, causing Exchange Online to trust identity assertions made with that credential. Administrative control of an on-premises Exchange server in a hybrid organization is required; the shared trust then extends the compromise into the cloud tenant.

CVSS severity8.0
High
EPSS probability7.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authentication in Microsoft Exchange Server hybrid deployments allows remote authenticated users to control connected Exchange Online. The Hybrid Configuration Wizard uploads the on-premises Auth Certificate to a shared first-party service principal, causing Exchange Online to trust identity assertions made with that credential. Administrative control of an on-premises Exchange server in a hybrid organization is required; the shared trust then extends the compromise into the cloud tenant.

The record

CVE
CVE-2025-53786
Published
Aug 6, 2025
Updated
Feb 26, 2026
Vendor
Microsoft
Product
Microsoft Exchange Server 2019 Cumulative Update 14
Classifications
CWE-287, T1550.001
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Aug 6, 2025CVE publishedPublication date reported by the CVE source.
  2. Feb 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=15.02.0.0 <15.02.1544.025

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Microsoft · Microsoft Exchange Server 2019 Cumulative Update 14version=15.02.0.0 <15.02.1544.025
Microsoft · Microsoft Exchange Server Subscription Edition RTMversion=15.02.0.0 <15.02.2562.017
Microsoft · Microsoft Exchange Server 2016 Cumulative Update 23version=15.01.0.0 <15.01.2507.055
Microsoft · Microsoft Exchange Server 2019 Cumulative Update 15version=15.02.0.0 <15.02.1748.024

Published CVSS scores

8.0Microsoft CorporationCVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1550.001Application Access Token

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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