Description
Use of uninitialized resource in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
Published: 2026-07-14
Score: 7.8 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Impact

A flaw in Microsoft Office Excel caused by the use of an uninitialized resource permits a user to run arbitrary code with the privileges of the current user. Classified as CWE‑908, the vulnerability provides a local code execution path that could be abused to elevate privileges or exfiltrate data on the victim machine.

Affected Systems

The affected products include Microsoft 365 Apps for Enterprise, Microsoft Excel 2016, Microsoft Office 2019, Microsoft Office 365 for Mac, Microsoft Office LTSC 2021, Microsoft Office LTSC 2024, Microsoft Office LTSC for Mac 2021, Microsoft Office LTSC for Mac 2024, and Office Online Server. Because the specific version ranges are not provided, all current releases of these products are considered vulnerable until a vendor update is released.

Risk and Exploitability

The CVSS score of 7.8 rates this vulnerability as high severity, yet the EPSS score of less than 1% indicates a very low current exploitation probability. The vulnerability is not listed in the CISA KEV catalog. The likely attack vector is local: a malicious or crafted Excel file must be opened by a user, or the attacker must have local access to deliver the file. There is no evidence of a remote exploitation path from the supplied data.

Generated by OpenCVE AI on July 31, 2026 at 06:38 UTC.

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

  • Download and install the Microsoft security update that addresses CVE-2026-55949 as soon as it becomes available.
  • Until the update is applied, prohibit users from opening unknown or untrusted Excel workbooks and enforce strict file-type filtering or application whitelisting in endpoint protection solutions.
  • Run Microsoft Office applications with the least privilege necessary for the task and monitor for anomalous execution that might indicate exploitation.

Generated by OpenCVE AI on July 31, 2026 at 06:38 UTC.

Tracking

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Advisories

No advisories yet.

History

Wed, 15 Jul 2026 12:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Tue, 14 Jul 2026 17:45:00 +0000

Type Values Removed Values Added
Description Use of uninitialized resource in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
Title Microsoft Excel Remote Code Execution Vulnerability
First Time appeared Microsoft
Microsoft 365 Apps
Microsoft excel 2016
Microsoft office 2019
Microsoft office 2021
Microsoft office 2024
Microsoft office 365
Microsoft office Macos 2021
Microsoft office Macos 2024
Weaknesses CWE-908
CPEs cpe:2.3:a:microsoft:365_apps:*:*:*:*:enterprise:*:*:*
cpe:2.3:a:microsoft:excel_2016:*:*:*:*:*:*:x86:*
cpe:2.3:a:microsoft:office_2019:*:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:office_2021:*:*:*:*:long_term_servicing_channel:*:*:*
cpe:2.3:a:microsoft:office_2021:*:*:*:*:ltsc:*:*:*
cpe:2.3:a:microsoft:office_2024:*:*:*:*:long_term_servicing_channel:*:*:*
cpe:2.3:a:microsoft:office_365:*:*:*:*:*:macos:*:*
cpe:2.3:a:microsoft:office_macos_2021:*:*:*:*:*:long_term_servicing_channel:*:*
cpe:2.3:a:microsoft:office_macos_2024:*:*:*:*:*:long_term_servicing_channel:*:*
Vendors & Products Microsoft
Microsoft 365 Apps
Microsoft excel 2016
Microsoft office 2019
Microsoft office 2021
Microsoft office 2024
Microsoft office 365
Microsoft office Macos 2021
Microsoft office Macos 2024
References
Metrics cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C'}


Subscriptions

Microsoft 365 Apps Excel 2016 Office 2019 Office 2021 Office 2024 Office 365 Office Macos 2021 Office Macos 2024
cve-icon MITRE

Status: PUBLISHED

Assigner: microsoft

Published:

Updated: 2026-08-03T22:57:31.787Z

Reserved: 2026-06-17T17:37:17.983Z

Link: CVE-2026-55949

cve-icon Vulnrichment

Updated: 2026-07-15T11:14:17.386Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-07-31T06:45:03Z

Weaknesses
  • CWE-908

    Use of Uninitialized Resource