Microsoft Security Update Guide · Office / Microsoft 365 Apps
Microsoft Excel 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 if a user takes part, for example by opening a link or file.
- CVSS 8.8 out of 10: high. 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 Office LTSC 2021 for 64-bit editions: KBRelease Notes
16.0.14334.20974 - Microsoft Office 365 for Mac: KBRelease Notes
- Microsoft 365 Apps for Enterprise for 32-bit Systems: KBRelease Notes
https://aka.ms/OfficeSecurityReleases - Office Online Server: KB5002928
16.0.10417.20228 - Microsoft 365 Apps for Enterprise for 64-bit Systems: KBRelease Notes
https://aka.ms/OfficeSecurityReleases - Microsoft Office LTSC 2024 for 32-bit editions: KBRelease Notes
16.0.17932.21056
- Microsoft Office LTSC 2021 for 64-bit editions: KBRelease Notes
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
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-125: Out-of-bounds Read
The program reads outside its allocated memory and can leak information. - CWE-20: Improper Input Validation
Input is not checked well enough before the software uses it.
Key facts
Released
13 okt 2026
Impact
Remote Code Execution
Max severity
Critical
Weakness
CVSS 3.1
8.8 / 7.7 (base / temporal)
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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 | Required |
| 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 Office LTSC 2021 for 64-bit editions | KBRelease Notes | 16.0.14334.20974 |
| Microsoft Office 365 for Mac | KBRelease Notes | — |
| Microsoft 365 Apps for Enterprise for 32-bit Systems | KBRelease Notes | https://aka.ms/OfficeSecurityReleases |
| Office Online Server | KB5002928 · Security Update | 16.0.10417.20228 |
| Microsoft 365 Apps for Enterprise for 64-bit Systems | KBRelease Notes | https://aka.ms/OfficeSecurityReleases |
| 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 for Mac 2024 | KBRelease Notes | — |
| Microsoft Office LTSC 2021 for 32-bit editions | KBRelease Notes | 16.0.14334.20974 |
| Microsoft Office LTSC for Mac 2021 | KBRelease Notes | — |
FAQ
- According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do?
- An attacker must send a user a malicious Office file and convince them to open it.
- Is the Preview Pane an attack vector for this vulnerability?
- No, the Preview Pane is not 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.
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.
