Microsoft Security Update Guide · Office / Microsoft 365 Apps
Microsoft Office Outlook Remote Code Execution Vulnerability
Published
What does this mean?
- Remote Code Execution. An attacker can run their own code on the system remotely. This is the most serious type: it can lead to taking over the system.
- It can be exploited over the network (including from the internet if the service is reachable there), without an account and without any user action.
- CVSS 9.8 out of 10: critical. Microsoft rates it Critical.
- 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 365 Apps for Enterprise for 32-bit Systems: KBRelease Notes
https://aka.ms/OfficeSecurityReleases - Microsoft 365 Apps for Enterprise for 64-bit Systems: KBRelease Notes
https://aka.ms/OfficeSecurityReleases - Microsoft Office 365 for Mac: KBRelease Notes
- Microsoft Office LTSC 2024 for 32-bit editions: KBRelease Notes
16.0.17932.21056 - Microsoft Office LTSC 2024 for 64-bit editions: KBRelease Notes
16.0.17932.21056 - Microsoft Office LTSC 2021 for 64-bit editions: KBRelease Notes
16.0.14334.20974
- Microsoft 365 Apps for Enterprise for 32-bit Systems: KBRelease Notes
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
Outlook Office / Microsoft 365 Apps
How do I check if I am affected?
Update the app
- Update the app through the App Store, Google Play or the app's own automatic updates.
- If you manage devices with Intune, check in the Intune admin center which devices still run an older version.
What kind of flaw is this?
- CWE-122: Heap-based Buffer Overflow
A heap buffer overflows, which can lead to running code.
Key facts
Released
13 okt 2026
Impact
Remote Code Execution
Max severity
Critical
Weakness
CVSS 3.1
9.8 / 8.5 (base / temporal)
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/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 | Network |
| Attack Complexity | Low |
| Privileges Required | None |
| 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 365 Apps for Enterprise for 32-bit Systems | KBRelease Notes | https://aka.ms/OfficeSecurityReleases |
| Microsoft 365 Apps for Enterprise for 64-bit Systems | KBRelease Notes | https://aka.ms/OfficeSecurityReleases |
| Microsoft Office 365 for Mac | KBRelease Notes | — |
| Microsoft Office LTSC 2024 for 32-bit editions | KBRelease Notes | 16.0.17932.21056 |
| Microsoft Office LTSC 2024 for 64-bit editions | KBRelease Notes | 16.0.17932.21056 |
| Microsoft Office LTSC 2021 for 64-bit editions | KBRelease Notes | 16.0.14334.20974 |
| Microsoft Office LTSC 2021 for 32-bit editions | KBRelease Notes | 16.0.14334.20974 |
| Microsoft Office LTSC for Mac 2024 | KBRelease Notes | — |
| Microsoft Office LTSC for Mac 2021 | KBRelease Notes | — |
FAQ
- Is the Preview Pane an attack vector for this vulnerability?
- Yes, the Preview Pane is an attack vector.
- Are the updates for the Microsoft Office LTSC for Mac currently available?
- The security update for Microsoft Office LTSC for Mac 2021 and 2024 are not immediately available. The updates will be released as soon as possible, and when they are available, customers will be notified via a revision to this CVE information.
- How could an attacker exploit this vulnerability?
- An attacker could send a specially crafted email message to a target user. Simply viewing the message in the Outlook Reading Pane could trigger the vulnerability, without the recipient opening the message or clicking anything in it. Successful exploitation could allow the attacker to execute code on the recipient's system. Network access is required; authentication and user interaction are not required.
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.
