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Privacy Statement Third-Party Cookies AcceptRejectManage cookies MSRC  Customer Guidance  Security Update Guide  Vulnerabilities  CVE-2026-66810 Microsoft Office Word Information Disclosure Vulnerability New On this page  CVE-2026-66810  Subscribe RSS PowerShell  API  CSAF Security Vulnerability Released: Aug 11, 2026 Assigning CNA Microsoft CVE.org link CVE-2026-66810  Impact Information Disclosure Max Severity Important Weakness CWE-122: Heap-based Buffer Overflow CVSS Source Microsoft Vector String CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C Metrics CVSS:3.1 5.5 / 4.8  Base score metrics: 5.5 / Temporal score metrics: 4.8  Expand all  Collapse all Metric Value   Base score metrics(8) Attack Vector Local Attack Complexity Low Privileges Required None User Interaction Required Scope Unchanged Confidentiality High 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 Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to disclose information 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 What type of information could be disclosed by this vulnerability? An attacker who successfully exploited this vulnerability could potentially read portions of process memory. Is the Preview Pane an attack vector for this vulnerability? No, the Preview Pane is not an attack vector. Acknowledgements Haein Lee with KAIST Hacking Lab Jeongmin Choi 𝕏 @ lmksecurity 0ccbbf129444eb66344ccafb92b00df4 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 Title: Release date, Content: Aug 11, 2026 Microsoft Office 365 for Mac - Information Disclosure Important Title: Knowledge Base Articles for Microsoft Office 365 for Mac, Content:, 1 link Release Notes  Title: Download Security Update for Microsoft Office 365 for Mac, Content:, 1 link Security Update  Title: Build numbers, Content: 16.112.26081010 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Aug 11, 2026 Microsoft Word 2016 (64-bit edition) - Information Disclosure Important Title: Knowledge Base Articles for Microsoft Word 2016 (64-bit edition), Content:, 1 link 5002901  Title: Download Security Update for Microsoft Word 2016 (64-bit edition), Content:, 1 link Security Update  Title: Build numbers, Content: 16.0.5565.1000 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Aug 11, 2026 Microsoft Word 2016 (32-bit edition) - Information Disclosure Important Title: Knowledge Base Articles for Microsoft Word 2016 (32-bit edition), Content:, 1 link 5002901  Title: Download Security Update for Microsoft Word 2016 (32-bit edition), Content:, 1 link Security Update  Title: Build numbers, Content: 16.0.5565.1000 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Aug 11, 2026 Microsoft Office LTSC for Mac 2024 - Information Disclosure Important 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: 16.112.26081010 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Aug 11, 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: Release date, Content: Aug 11, 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: Release date, Content: Aug 11, 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: Release date, Content: Aug 11, 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: Release date, Content: Aug 11, 2026 Microsoft Office LTSC for Mac 2021 - Information Disclosure Important 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: 16.112.26081010 Title: Assigning CNA, Content: Microsoft Title: Release date, Content: Aug 11, 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: Release date, Content: Aug 11, 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: Release date, Content: Aug 11, 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: Release date, Content: Aug 11, 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 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. 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 Aug 11, 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 Privacy & Cookies