CVE-2026-55899

Published: Jul 14, 2026Modified: Jul 16, 2026

7.8

Vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploitability: 1.8 / Impact: 5.9

Source: secure@microsoft.com (Secondary)

Description

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

Affected (14)

Products: Microsoft: 365 Apps, Excel, Microsoft 365, Office 2019, Office 2021, Office 2024, Office Online Server

7 products

Office Online Server

Configuration A

14 vulnerable

Vulnerable Software	Affected Versions
Microsoft 365 Apps	All versions
Microsoft 365 Apps	All versions
Microsoft Excel	Version 2016
Microsoft Excel	Version 2016
Microsoft Microsoft 365	All versions
Microsoft Office 2019	All versions
Microsoft Office 2019	All versions
Microsoft Office 2021	All versions
Microsoft Office 2021	All versions
Microsoft Office 2021	All versions
Microsoft Office 2024	All versions
Microsoft Office 2024	All versions
Microsoft Office 2024	All versions
Microsoft Office Online Server	Before 16.0.10417.20175

Related CWEs

Stack-based Buffer Overflow

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

References (1)

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55899

Source: secure@microsoft.com

PatchVendor Advisory

Timeline

No history available yet.