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Microsoft Outlook and Word Remote Code Execution Vulnerability

CVE-2026-78510 is a remote code execution vulnerability in Microsoft Office (rated Critical, CVSS 8.4).

1 version

Facts

Microsoft id
CVE-2026-78510
Products
Microsoft Office
Severity
Critical
Impact
Remote Code Execution
CVSS
8.4
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Exploited
No
Publicly disclosed
No
Exploitability
Exploitation Less Likely
Customer action required
Yes
Release
2026-Sep
Assigned by
Microsoft
Weakness
CWE-122: Heap-based Buffer Overflow
MSRC revision
2.1
Status pages
Microsoft 365 apps status
First captured by us
(from our first import of this list)
Microsoft last modified
Source
Security updates · open the original at Microsoft

Microsoft's revision notes

  1. Revision 1.0, 2026-09-08: Information published.
  2. Revision 1.2, 2026-09-21: Updated CVE title. This is an informational change only.
  3. Revision 2.0, 2026-09-17: Microsoft is announcing the availability of the security updates for Microsoft Office for Mac.
  4. Revision 2.1, 2026-09-25: Updated CVE title and CVSS Score. This is an informational change only.

Microsoft says

Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.

Security updates,

Read Microsoft's full post

What Microsoft changed

One version so far. If Microsoft edits it, each change shows here with what was removed and added.

  1. First version we captured ·

    The text as we first saw it

    Seen by us · Microsoft's timestamp · Microsoft's page

Mentioning the same Microsoft ids

Other changes for Microsoft 365 apps

Last updated