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Privacy Statement Third-Party Cookies Accept Reject Manage cookies MSRC  Customer Guidance  Security Update Guide  Vulnerabilities  CVE-2026-40421 Microsoft Word Information Disclosure Vulnerability New On this page  CVE-2026-40421  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: May 12, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-40421  Impact Information Disclosure Max Severity Important Weakness CWE-73: External Control of File Name or Path CVSS Source Microsoft Vector String CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N/E:U/RL:O/RC:C Metrics CVSS:3.1 4.3 / 3.8  Base score metrics: 4.3 / Temporal score metrics: 3.8  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Network Attack Complexity Low Privileges Required None User Interaction Required Scope Unchanged Confidentiality Low Integrity None Availability None   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 External control of file name or path in Microsoft Office Word allows an unauthorized attacker to disclose information over a network. 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 According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do? An attacker must send a user a malicious Office file and convince them to open it. What type of information could be disclosed by this vulnerability? Exploiting this vulnerability could allow the disclosure of NTLM hashes. According to the CVSS metrics, successful exploitation of this vulnerability could lead to some loss of confidentiality (C:L),but lead to no loss of availability (A:N) and integrity (I:N)? What does that mean for this vulnerability? An attacker who successfully exploited the vulnerability could view some sensitive information (Confidentiality) but not all resources within the impacted component may be divulged to the attacker. The attacker cannot make changes to disclosed information (Integrity) or limit access to the resource (Availability). Is the Preview Pane an attack vector for this vulnerability? No, the Preview Pane is not an attack vector. Acknowledgements tiebuchen 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 Word 2016 (64-bit edition) - Information Disclosure Important Title: Knowledge Base Articles for Microsoft Word 2016 (64-bit edition), Content:, 1 link 5002858  Title: Download Security Update for Microsoft Word 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 Word 2016 (32-bit edition) - Information Disclosure Important Title: Knowledge Base Articles for Microsoft Word 2016 (32-bit edition), Content:, 1 link 5002858  Title: Download Security Update for Microsoft Word 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 2024 for 64-bit editions - Information Disclosure Important 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 - Information Disclosure Important 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 - Information Disclosure Important 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 - Information Disclosure Important 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 Title: Release date, Content: May 12, 2026 Microsoft 365 Apps for Enterprise for 64-bit Systems - Information Disclosure Important 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 - Information Disclosure Important 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 - Information Disclosure Important 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 - Information Disclosure Important 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 All results loaded Loaded all 10 rows Disclaimer The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply. Revisions version revisionDate description 1.0 May 12, 2026 Information published.  How satisfied are you with the MSRC Security Update Guide? Rating  Broken  Bad  Below average  Average  Great!  Your Privacy Choices Consumer Health Privacy