CVE-2026-64914 Overview
CVE-2026-64914 is a heap-based buffer overflow vulnerability in Microsoft Office Access. The flaw allows an unauthorized attacker to execute code locally on a targeted system. Exploitation requires user interaction, typically by opening a crafted Access database file. Successful exploitation yields code execution with the privileges of the current user and impacts confidentiality, integrity, and availability. The weakness is classified under CWE-122: Heap-based Buffer Overflow. Microsoft published the advisory on August 11, 2026, and released fixes through its security update channel.
Critical Impact
An attacker who convinces a user to open a malicious Access file can execute arbitrary code in the user's context, leading to full compromise of the local session.
Affected Products
- Microsoft Office Access (versions addressed in the Microsoft Security Update for CVE-2026-64914)
Discovery Timeline
- 2026-08-11 - CVE-2026-64914 published to NVD
- 2026-08-12 - Last updated in NVD database
Technical Details for CVE-2026-64914
Vulnerability Analysis
CVE-2026-64914 is a heap-based buffer overflow (CWE-122) inside Microsoft Office Access. The issue is triggered when Access parses attacker-controlled content within a database file. Insufficient bounds checking during parsing allows the writing of data past the end of a heap-allocated buffer. This corrupts adjacent heap structures and can be leveraged to redirect execution flow.
The attack vector is local and requires user interaction, meaning the victim must open the malicious file. Once opened, Access executes attacker-controlled code with the privileges of the invoking user. High impact ratings apply to confidentiality, integrity, and availability, because arbitrary code execution allows data theft, tampering, and denial of service on the host.
Root Cause
The root cause is improper validation of data length or field boundaries in an Access file-parsing routine. Access allocates a heap buffer sized for expected input but does not enforce those limits when copying attacker-supplied records. This mismatch permits an out-of-bounds heap write, which is the defining characteristic of CWE-122.
Attack Vector
An attacker crafts a malicious Access database file, for example an .accdb or .mdb file, and delivers it through phishing, a compromised web download, or a shared file store. When the victim opens the file with a vulnerable version of Access, parsing triggers the heap overflow. The attacker can then execute code, install persistence, or pivot to further internal resources. No prior authentication is required against the application itself.
No public proof-of-concept exploit and no known in-the-wild exploitation have been reported at the time of publication. See the Microsoft Security Update for CVE-2026-64914 for authoritative technical details.
Detection Methods for CVE-2026-64914
Indicators of Compromise
- Unexpected MSACCESS.EXE child processes such as cmd.exe, powershell.exe, rundll32.exe, or regsvr32.exe.
- Access database files (.accdb, .mdb, .accde) delivered via email or downloaded from untrusted domains and opened shortly before suspicious process activity.
- Access process crashes with heap corruption exceptions in Windows Error Reporting logs.
Detection Strategies
- Hunt for process-lineage anomalies where MSACCESS.EXE spawns scripting or living-off-the-land binaries.
- Monitor for outbound network connections initiated by MSACCESS.EXE, which is uncommon in most environments.
- Alert on file writes to autorun and startup locations that follow the opening of an Access document.
Monitoring Recommendations
- Ingest Microsoft Office telemetry and endpoint process events into a SIEM or data lake for behavioral correlation.
- Track patch state of Microsoft Office Access across the estate and flag hosts that lag behind the August 2026 update cycle.
- Review mail gateway logs for inbound .accdb and .mdb attachments and validate against expected business use.
How to Mitigate CVE-2026-64914
Immediate Actions Required
- Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-64914 to all systems with Microsoft Office Access installed.
- Block or quarantine inbound Access database attachments (.accdb, .mdb, .accde) at the mail gateway until patching is complete.
- Restrict local user privileges so that a successful exploit does not yield administrative access.
Patch Information
Microsoft has issued fixes through the Microsoft Update channel. Refer to the Microsoft Security Update for CVE-2026-64914 for the specific build numbers that address the flaw across supported Office and Microsoft 365 Apps channels. Deploy updates using Microsoft Update, Windows Server Update Services (WSUS), Microsoft Intune, or Configuration Manager per organizational policy.
Workarounds
- Enable Protected View and Office File Block policy for legacy Access file formats to force review before opening.
- Use Attack Surface Reduction (ASR) rules that block Office applications from creating child processes.
- Educate users to avoid opening unsolicited Access database files and to report suspicious attachments.
# Example: enforce ASR rule blocking Office child processes via PowerShell
Set-MpPreference -AttackSurfaceReductionRules_Ids D4F940AB-401B-4EFC-AADC-AD5F3C50688A `
-AttackSurfaceReductionRules_Actions Enabled
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
