Microsoft Security Update Guide · Exchange
Microsoft Exchange Server Elevation of Privilege Vulnerability
Published · updated 23 jun 2026
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 over the network (including from the internet if the service is reachable there), with an ordinary user account and without any user action.
- CVSS 8.8 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: KB5103214
15.02.1544.043 - Microsoft Exchange Server 2016 Cumulative Update 23: KB5103215
15.01.2507.071 - Microsoft Exchange Server 2019 Cumulative Update 15: KB5103213
15.02.1748.048 - Microsoft Exchange Server Subscription Edition RTM: KB5103212
15.02.2562.045
- Microsoft Exchange Server 2019 Cumulative Update 14: KB5103214
Server-side request forgery (ssrf) in Microsoft Exchange Server allows an authorized attacker to elevate privileges over a network.
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.
What kind of flaw is this?
- CWE-918: Server-Side Request Forgery (SSRF)
The server can be made to send requests to other systems on the attacker's behalf (server-side request forgery).
Key facts
Released
9 jun 2026
Last revised
23 jun 2026 (v1.1)
Impact
Elevation of Privilege
Max severity
Important
Weakness
CVSS 3.1
8.8 / 7.7 (base / temporal)
Vector string
CVSS:3.1/AV:N/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 Unlikely
Customer action required
Yes
Links
CVSS metrics
| Base score metrics | |
|---|---|
| Attack Vector | Network |
| 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 | KB5103214 | 15.02.1544.043 |
| Microsoft Exchange Server 2016 Cumulative Update 23 | KB5103215 | 15.01.2507.071 |
| Microsoft Exchange Server 2019 Cumulative Update 15 | KB5103213 | 15.02.1748.048 |
| Microsoft Exchange Server Subscription Edition RTM | KB5103212 · Security Update | 15.02.2562.045 |
FAQ
- What privileges could be gained by an attacker who successfully exploited the vulnerability?
- An attacker could gain elevated privileges beyond those normally available to them, allowing actions such as accessing restricted information or performing operations that are typically limited to more highly privileged users or administrators.
- How could an attacker exploit this vulnerability?
- An attacker with a low-privilege user account and an assigned mailbox, could exploit weaknesses in how Exchange validates requests and identity tokens to impersonate another user. By doing so, the attacker could then access mailboxes through Exchange services as if they were that user.
Revisions
| Version | Date | Note |
|---|---|---|
| 1.1 | 23 jun 2026 | Acknowledgement added. This is an informational change only. |
| 1 | 9 jun 2026 | Information published. |
What changed in Microsoft 365 this week? →
View at Microsoft → ← All security advisories
Source: Microsoft Security Update Guide. 365Fanatic is not affiliated with Microsoft.
