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Privacy Statement Third-Party Cookies Accept Reject Manage cookies MSRC  Customer Guidance  Security Update Guide  Vulnerabilities  CVE-2026-40363 Microsoft Office Remote Code Execution Vulnerability New On this page  CVE-2026-40363  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: May 12, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-40363  Impact Remote Code Execution Max Severity Critical Weakness CWE-122: Heap-based Buffer Overflow CVSS Source Microsoft Vector String 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 Metrics CVSS:3.1 8.4 / 7.3  Base score metrics: 8.4 / Temporal score metrics: 7.3  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Local Attack Complexity Low Privileges Required None User Interaction None Scope Unchanged Confidentiality High Integrity High Availability High   Temporal score metrics(3) Exploit Code Maturity Unproven Remediation Level Official Fix Report Confidence Confirmed Please see Common Vulnerability Scoring System for more information on the definition of these metrics. Executive Summary Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally. Exploitability The following table provides an exploitability assessment for this vulnerability at the time of original publication. Publicly disclosed No Exploited No Exploitability assessment Exploitation Less Likely FAQ Is the Preview Pane an attack vector for this vulnerability? Yes, the Preview Pane is an attack vector. According to the CVSS metric, the attack vector is local (AV:L). Why does the CVE title indicate that this is a remote code execution? The word Remote in the title refers to the location of the attacker. This type of exploit is sometimes referred to as Arbitrary Code Execution (ACE). The attack itself is carried out locally. This means an attacker or victim needs to execute code from the local machine to exploit the vulnerability. Acknowledgements Jeongmin Choi 𝕏 @ lmksecurity with S2W https://s2w.inc/ko/ Microsoft recognizes the efforts of those in the security community who help us protect customers through coordinated vulnerability disclosure. See Acknowledgements for more information. Security Updates To determine the support lifecycle for your software, see the Microsoft Support Lifecycle. Release date Descending  Edit columns  Download  Filters  Product Family  Max Severity  Impact  Platform   Clear Release date  Product Platform Impact Max Severity Article Download Build Number Assigning CNA Customer Action Required Title: Release date, Content: May 12, 2026 Microsoft Office LTSC for Mac 2021 - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office LTSC for Mac 2021, Content:, 1 link Release Notes  Title: Download Security Update for Microsoft Office LTSC for Mac 2021, Content:, 1 link Security Update  Title: Build numbers, Content: 16.109.26051019 Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft 365 Apps for Enterprise for 64-bit Systems - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft 365 Apps for Enterprise for 64-bit Systems, Content:, 1 link Click to Run  Title: Download Security Update for Microsoft 365 Apps for Enterprise for 64-bit Systems, Content:, 1 link Security Update Title: Build numbers, Content: https://aka.ms/OfficeSecurityReleases Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft 365 Apps for Enterprise for 32-bit Systems - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft 365 Apps for Enterprise for 32-bit Systems, Content:, 1 link Click to Run  Title: Download Security Update for Microsoft 365 Apps for Enterprise for 32-bit Systems, Content:, 1 link Security Update Title: Build numbers, Content: https://aka.ms/OfficeSecurityReleases Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office 2019 for 64-bit editions - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office 2019 for 64-bit editions, Content:, 1 link Click to Run  Title: Download Security Update for Microsoft Office 2019 for 64-bit editions, Content:, 1 link Security Update Title: Build numbers, Content: https://aka.ms/OfficeSecurityReleases Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office 2019 for 32-bit editions - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office 2019 for 32-bit editions, Content:, 1 link Click to Run  Title: Download Security Update for Microsoft Office 2019 for 32-bit editions, Content:, 1 link Security Update Title: Build numbers, Content: https://aka.ms/OfficeSecurityReleases Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office for Android - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office for Android, Content:, 1 link Release Notes  Title: Download Security Update for Microsoft Office for Android, Content:, 1 link Security Update  Title: Build numbers, Content: 16.0.19822.20190 Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office 2016 (64-bit edition) - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office 2016 (64-bit edition), Content:, 1 link 5002866  Title: Download Security Update for Microsoft Office 2016 (64-bit edition), Content:, 1 link Security Update  Title: Build numbers, Content: 16.0.5552.1000 Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office 2016 (32-bit edition) - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office 2016 (32-bit edition), Content:, 1 link 5002866  Title: Download Security Update for Microsoft Office 2016 (32-bit edition), Content:, 1 link Security Update  Title: Build numbers, Content: 16.0.5552.1000 Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office LTSC for Mac 2024 - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office LTSC for Mac 2024, Content:, 1 link Release Notes  Title: Download Security Update for Microsoft Office LTSC for Mac 2024, Content:, 1 link Security Update  Title: Build numbers, Content: 16.109.26051019 Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office LTSC 2024 for 64-bit editions - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office LTSC 2024 for 64-bit editions, Content:, 1 link Click to Run  Title: Download Security Update for Microsoft Office LTSC 2024 for 64-bit editions, Content:, 1 link Security Update Title: Build numbers, Content: https://aka.ms/OfficeSecurityReleases Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office LTSC 2024 for 32-bit editions - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office LTSC 2024 for 32-bit editions, Content:, 1 link Click to Run  Title: Download Security Update for Microsoft Office LTSC 2024 for 32-bit editions, Content:, 1 link Security Update Title: Build numbers, Content: https://aka.ms/OfficeSecurityReleases Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office LTSC 2021 for 32-bit editions - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office LTSC 2021 for 32-bit editions, Content:, 1 link Click to Run  Title: Download Security Update for Microsoft Office LTSC 2021 for 32-bit editions, Content:, 1 link Security Update Title: Build numbers, Content: https://aka.ms/OfficeSecurityReleases Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required Title: Release date, Content: May 12, 2026 Microsoft Office LTSC 2021 for 64-bit editions - Remote Code Execution Critical Title: Knowledge Base Articles for Microsoft Office LTSC 2021 for 64-bit editions, Content:, 1 link Click to Run  Title: Download Security Update for Microsoft Office LTSC 2021 for 64-bit editions, Content:, 1 link Security Update Title: Build numbers, Content: https://aka.ms/OfficeSecurityReleases Title: Assigning CNA, Content: Microsoft Title: Customer action required, Content: Required All results loaded Loaded all 13 rows Disclaimer The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. 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