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Microsoft Security Update Guide · Office / Microsoft 365 Apps

Microsoft Office OneNote Remote Code Execution Vulnerability

Microsoft · EN CVE-2026-102858 Important Action required CVSS 8.8

Published

SummaryDetailedSecurity

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 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
    • Microsoft Office LTSC for Mac 2021: KBRelease Notes
    • Microsoft Office LTSC for Mac 2024: KBRelease Notes

Microsoft Office OneNote · Remote Code Execution

Heap-based buffer overflow in Microsoft Office OneNote allows an unauthorized attacker to execute code over a network.

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?

Key facts

Released
13 okt 2026
Impact
Remote Code Execution
Max severity
Important
Weakness
CWE-122: Heap-based Buffer Overflow
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:C
Publicly disclosed
No
Exploited
No
Exploitability assessment
Exploitation Unlikely
Customer action required
Yes
Links
Microsoft Security Update Guide · CVE.org

CVSS metrics

Base score metrics
Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionRequired
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
Temporal score metrics
Exploit Code MaturityUnproven
Remediation LevelOfficial Fix
Report ConfidenceConfirmed

Affected products and updates

ProductUpdateBuild
Microsoft Office 365 for MacKBRelease Notes—
Microsoft Office LTSC for Mac 2021KBRelease Notes—
Microsoft Office LTSC for Mac 2024KBRelease Notes—

FAQ

According to the CVSS metric, the attack vector is network (AV:N) and user interaction is required (UI:R). What is the target context of the remote code execution?
This attack requires a user to open a specially crafted file from the attacker to initiate remote code execution.
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

VersionDateNote
113 okt 2026Information published.

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Source: Microsoft Security Update Guide. 365Fanatic is not affiliated with Microsoft.