Full Report
Microsoft security advisory (AV26-1001)
Analysis Summary
# Vulnerability: Microsoft Exchange Server Elevation of Privilege
## CVE Details
- **CVE ID:** CVE-2026-96940
- **CVSS Score:** Not explicitly listed in source (Typically High for Exchange EoP)
- **CWE:** CWE-269 (Improper Privilege Management) / Elevation of Privilege
## Affected Systems
- **Products:** Microsoft Exchange Server
- **Versions:**
- Exchange Server 2016 Cumulative Update 23: Prior to 15.01.2507.075
- Exchange Server 2019 Cumulative Update 14: Prior to 15.02.1544.048
- Exchange Server 2019 Cumulative Update 15: Prior to 15.02.1748.053
- Exchange Server Subscription Edition (SE) RTM: Prior to 15.02.2562.053
- **Configurations:** Systems running the listed Cumulative Updates (CU) without the October 2026 security patches.
## Vulnerability Description
This is an Elevation of Privilege (EoP) vulnerability within Microsoft Exchange Server. While technical specifics regarding the exact mechanism (e.g., NTLM relay or RBAC bypass) are not detailed in the brief advisory, EoP flaws in Exchange typically allow an attacker with standard user access to gain administrative or SYSTEM-level privileges on the mail server.
## Exploitation
- **Status:** Not explicitly stated as exploited in the wild (refer to MSRC for real-time telemetry updates).
- **Complexity:** Medium (Typical for Exchange EoP requiring authenticated access).
- **Attack Vector:** Network.
## Impact
- **Confidentiality:** High (Potential access to all mailboxes and sensitive data).
- **Integrity:** High (Ability to modify server configurations or user permissions).
- **Availability:** Low to Medium (Primary impact is unauthorized access rather than service disruption).
## Remediation
### Patches
Microsoft has released the following security updates to address this vulnerability:
- **Exchange Server 2016 CU23:** Update to version 15.01.2507.075 or later.
- **Exchange Server 2019 CU14:** Update to version 15.02.1544.048 or later.
- **Exchange Server 2019 CU15:** Update to version 15.02.1748.053 or later.
- **Exchange Server SE RTM:** Update to version 15.02.2562.053 or later.
### Workarounds
- No specific workarounds are provided in the advisory; applying the security update is the recommended course of action.
- Ensure "Extended Protection for Authentication" (EPA) is enabled on all Exchange directories as a general best practice for mitigating EoP risks.
## Detection
- Monitor for unusual administrative activity or changes to Exchange Role-Based Access Control (RBAC) settings.
- Review Exchange audit logs for unauthorized elevation attempts.
- Use the Microsoft Exchange Server Health Checker script to verify patch levels.
## References
- Microsoft Security Advisory (AV26-1001): hxxps[://]www.cyber.gc.ca/en/alerts-advisories/microsoft-security-advisory-av26-1001
- Microsoft MSRC CVE-2026-96940: hxxps[://]msrc.microsoft.com/update-guide/vulnerability/CVE-2026-96940
- Microsoft Security Update Guide: hxxps[://]msrc.microsoft.com/update-guide/vulnerability