Microsoft Security Update Guide · Exchange
Microsoft Exchange Server Elevation of Privilege Vulnerability
Published
What does this mean?
- Elevation of Privilege. An attacker can gain more rights than they should have, for example admin rights.
- It can be exploited with access to the device itself, with an ordinary user account and without any user action.
- CVSS 7.8 out of 10: high. Microsoft rates it Important.
- No attacks reported; Microsoft expects exploitation to be less likely.
- What should you do? Install the security update for the version you run (or a later cumulative update):
- Microsoft Exchange Server 2019 Cumulative Update 14: KB5128897
15.02.1544.050 - Microsoft Exchange Server Subscription Edition RTM: KB5128895
15.02.2562.056 - Microsoft Exchange Server 2016 Cumulative Update 23: KB5128898
15.01.2507.077 - Microsoft Exchange Server 2019 Cumulative Update 15: KB5128896
15.02.1748.055
- Microsoft Exchange Server 2019 Cumulative Update 14: KB5128897
Inclusion of functionality from untrusted control sphere in Microsoft Exchange Server allows an authorized attacker to elevate privileges locally.
How do I check if I am affected?
Exchange Server: check and update
- Check your server versions in the Exchange Management Shell:
Get-ExchangeServer | Format-List Name,AdminDisplayVersion - Microsoft's Exchange Health Checker (CSS-Exchange on GitHub) shows which updates are missing per server.
- Install the security update (SU) for the CU you run. Microsoft updates Exchange Online.
Key facts
Released
13 okt 2026
Impact
Elevation of Privilege
Max severity
Important
Weakness
CVSS 3.1
7.8 / 6.8 (base / temporal)
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:CPublicly disclosed
No
Exploited
No
Exploitability assessment
Exploitation Less Likely
Customer action required
Yes
Links
CVSS metrics
| Base score metrics | |
|---|---|
| Attack Vector | Local |
| Attack Complexity | Low |
| Privileges Required | Low |
| User Interaction | None |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity | High |
| Availability | High |
| Temporal score metrics | |
| Exploit Code Maturity | Unproven |
| Remediation Level | Official Fix |
| Report Confidence | Confirmed |
Affected products and updates
| Product | Update | Build |
|---|---|---|
| Microsoft Exchange Server 2019 Cumulative Update 14 | KB5128897 | 15.02.1544.050 |
| Microsoft Exchange Server Subscription Edition RTM | KB5128895 · Security Update | 15.02.2562.056 |
| Microsoft Exchange Server 2016 Cumulative Update 23 | KB5128898 | 15.01.2507.077 |
| Microsoft Exchange Server 2019 Cumulative Update 15 | KB5128896 | 15.02.1748.055 |
FAQ
- What privileges could be gained by an attacker who successfully exploited this vulnerability?
- An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.
Revisions
| Version | Date | Note |
|---|---|---|
| 1 | 13 okt 2026 | Information published. |
This is in the weekly digest for week 42: everything that changed in Microsoft 365 this week. →
View at Microsoft → ← All security advisories
Source: Microsoft Security Update Guide. 365Fanatic is not affiliated with Microsoft.
