CVE-2026-45461 Overview
CVE-2026-45461 is a heap-based buffer overflow vulnerability in Microsoft Office that enables an unauthorized attacker to execute code locally. The flaw is classified under [CWE-416] Use After Free, indicating improper memory management during Office document processing. Successful exploitation grants attackers the privileges of the current user, allowing arbitrary code execution on the affected system.
Microsoft published the advisory on June 9, 2026. The vulnerability requires local attack vector access but no privileges and no user interaction to exploit. The EPSS score stands at 0.06% with a percentile of 19.07, indicating low observed exploitation activity at this time.
Critical Impact
Attackers can execute arbitrary code with full impact on confidentiality, integrity, and availability of the affected host.
Affected Products
- Microsoft Office (specific versions detailed in the Microsoft Security Update)
Discovery Timeline
- 2026-06-09 - CVE CVE-2026-45461 published to NVD
- 2026-06-09 - Last updated in NVD database
Technical Details for CVE-2026-45461
Vulnerability Analysis
The vulnerability is a heap-based buffer overflow rooted in a use-after-free condition [CWE-416] within Microsoft Office. When Office parses a malformed document, the application references heap memory that has already been freed. An attacker who controls the layout of the freed heap chunk can redirect execution flow to attacker-supplied data.
Exploitation results in arbitrary code execution in the context of the user running Office. Because the impact extends to confidentiality, integrity, and availability, an attacker can read sensitive files, modify documents, and disrupt application functionality. The local attack vector indicates the malicious content must be processed on the target machine, typically by opening a weaponized Office document.
Root Cause
The root cause is improper object lifetime management in Office's document parsing logic. A code path frees a heap object while another reference to the same memory remains active. Subsequent dereference of the dangling pointer corrupts adjacent heap metadata, enabling controlled memory writes.
Attack Vector
An attacker delivers a crafted Office document through email, file share, or web download. When the document is opened, Office triggers the vulnerable parsing path. The heap layout is groomed by embedded objects within the document, allowing the attacker to place controlled data adjacent to the freed object. Code execution follows once Office references the freed memory.
No proof-of-concept code has been published for this vulnerability. Refer to the Microsoft Security Update CVE-2026-45461 for vendor-confirmed technical details.
Detection Methods for CVE-2026-45461
Indicators of Compromise
- Unexpected child processes spawned by Office applications such as WINWORD.EXE, EXCEL.EXE, or POWERPNT.EXE launching cmd.exe, powershell.exe, or rundll32.exe.
- Office process crashes accompanied by Windows Error Reporting events referencing heap corruption or access violations.
- Suspicious Office document attachments containing embedded objects, ActiveX controls, or unusually large OLE streams.
Detection Strategies
- Monitor for anomalous memory allocation patterns and heap corruption events originating from Office processes.
- Correlate document open events with subsequent network connections, file writes to %TEMP%, or registry persistence modifications.
- Apply behavioral detection rules that flag Office processes performing code injection or loading unsigned DLLs.
Monitoring Recommendations
- Enable Windows Defender Attack Surface Reduction (ASR) rules that block Office from creating child processes and executable content.
- Forward Office telemetry and Sysmon events to a centralized SIEM for correlation across endpoints.
- Track inbound email attachments and shared documents for known malicious file hashes and unusual macro content.
How to Mitigate CVE-2026-45461
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update CVE-2026-45461 advisory across all affected Office installations.
- Inventory Office deployments and prioritize patching systems handling externally-sourced documents.
- Educate users to avoid opening unsolicited Office attachments and to report suspicious files.
Patch Information
Microsoft has published the patch through its monthly security update channel. Administrators should deploy the update via Windows Update, Microsoft Update Catalog, or enterprise patch management tooling. Validate patch deployment status by querying installed update KBs across the fleet.
Workarounds
- Enable Protected View for documents originating from the internet, email attachments, and unsafe locations.
- Configure Office to block macros in files from the internet via Group Policy.
- Deploy ASR rules to prevent Office applications from injecting code into other processes or creating child executables.
# Configuration example: Enforce Protected View via Group Policy registry keys
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableInternetFilesInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableAttachmentsInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableUnsafeLocationsInPV /t REG_DWORD /d 0 /f
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
