Microsoft Security Update Guide · Office / Microsoft 365 Apps
Microsoft Excel Information Disclosure Vulnerability
Published · updated 17 sep 2026
What does this mean?
- Information Disclosure. An attacker can see information that is not meant for them.
- It can be exploited with access to the device itself, without an account and if a user takes part, for example by opening a link or file.
- CVSS 5.5 out of 10: medium. 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 Office 365 for Mac: KBRelease Notes
16.113.26091433 - Microsoft Office 2016 (64-bit edition): KB5002904
16.0.5569.1003 - Microsoft Office 2016 (32-bit edition): KB5002904
16.0.5569.1003 - Microsoft Excel 2016 (32-bit edition): KB5002914
16.0.5569.1003 - Microsoft Excel 2016 (64-bit edition): KB5002914
16.0.5569.1003 - Microsoft Office LTSC for Mac 2024: KBRelease Notes
16.113.26091433
- Microsoft Office 365 for Mac: KBRelease Notes
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information locally.
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.
Key facts
Released
8 sep 2026
Last revised
17 sep 2026 (v2)
Impact
Information Disclosure
Max severity
Important
Weakness
CVSS 3.1
5.5 / 4.8 (base / temporal)
Vector string
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/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 | Local |
| Attack Complexity | Low |
| Privileges Required | None |
| User Interaction | Required |
| Scope | Unchanged |
| Confidentiality | High |
| Integrity | None |
| Availability | None |
| Temporal score metrics | |
| Exploit Code Maturity | Unproven |
| Remediation Level | Official Fix |
| Report Confidence | Confirmed |
Affected products and updates
| Product | Update | Build |
|---|---|---|
| Microsoft Office 365 for Mac | KBRelease Notes · Security Update | 16.113.26091433 |
| Microsoft Office 2016 (64-bit edition) | KB5002904 · Security Update | 16.0.5569.1003 |
| Microsoft Office 2016 (32-bit edition) | KB5002904 · Security Update | 16.0.5569.1003 |
| Microsoft Excel 2016 (32-bit edition) | KB5002914 · Security Update | 16.0.5569.1003 |
| Microsoft Excel 2016 (64-bit edition) | KB5002914 · Security Update | 16.0.5569.1003 |
| Microsoft Office LTSC for Mac 2024 | KBRelease Notes · Security Update | 16.113.26091433 |
| Microsoft Office LTSC 2024 for 64-bit editions | KBRelease Notes | 16.0.17932.20976 |
| Microsoft Office LTSC 2024 for 32-bit editions | KBRelease Notes | 16.0.17932.20976 |
| Microsoft Office LTSC 2021 for 32-bit editions | KBRelease Notes | 16.0.14334.20906 |
| Microsoft Office LTSC 2021 for 64-bit editions | KBRelease Notes | 16.0.14334.20906 |
| Microsoft Office LTSC for Mac 2021 | KBRelease Notes · Security Update | 16.113.26091433 |
| Microsoft 365 Apps for Enterprise for 64-bit Systems | KBRelease Notes | 16.0.20326.20138 |
| Microsoft 365 Apps for Enterprise for 32-bit Systems | KBRelease Notes | 16.0.20326.20138 |
| Microsoft Office 2019 for 64-bit editions | KBRelease Notes | 16.0.10417.20207 |
| Microsoft Office 2019 for 32-bit editions | KBRelease Notes | 16.0.10417.20207 |
FAQ
- Is the Preview Pane an attack vector for this vulnerability?
- No, the Preview Pane is not an attack vector.
- What type of information could be disclosed by this vulnerability?
- The type of information that could be disclosed if an attacker successfully exploited this vulnerability is uninitialized heap memory.
- Are the updates for Microsoft Office LTSC for Mac 2021 and 2024 currently available?
- Yes. As of September 16, 2026, the security update for Microsoft Office LTSC for Mac 2021, 2024 and Microsoft Office 365 for Mac are available. Customers running Microsoft Office LTSC for Mac 2021, 2024 and Microsoft Office 365 for Mac should ensure the update is installed to be protected from this vulnerability.
Revisions
| Version | Date | Note |
|---|---|---|
| 2 | 17 sep 2026 | Microsoft is announcing the availability of the security updates for Microsoft Office for Mac. Customers running affected Mac software should install the update for their product to be protected from this vulnerability. Customers running other Microsoft Office software do not need to take any action. See the Release Notes for more information and download links. |
| 1 | 8 sep 2026 | Information published. |
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Source: Microsoft Security Update Guide. 365Fanatic is not affiliated with Microsoft.
