CVE-2026-45485 Overview
CVE-2026-45485 is an out-of-bounds read vulnerability in Microsoft Office that allows a local, unauthorized attacker to disclose information. The flaw is classified under [CWE-125] and requires user interaction to trigger, typically through opening a malicious document. Successful exploitation enables an attacker to read memory contents outside intended buffer boundaries, potentially exposing sensitive process data. Microsoft published the security update on June 9, 2026.
Critical Impact
Local information disclosure through memory contents read outside allocated buffer boundaries when a victim opens a crafted Office document.
Affected Products
- Microsoft Office (specific versions listed in Microsoft's advisory)
Discovery Timeline
- 2026-06-09 - CVE-2026-45485 published to NVD
- 2026-06-09 - Last updated in NVD database
Technical Details for CVE-2026-45485
Vulnerability Analysis
The vulnerability is an out-of-bounds read [CWE-125] within Microsoft Office. The flaw occurs when Office parses a crafted document and reads memory beyond the boundary of an allocated buffer. The attacker does not require authentication, but user interaction is necessary, meaning the victim must open or preview a malicious file.
Impact is limited to confidentiality. The vulnerability does not modify data and does not directly affect system availability. An attacker who successfully exploits this issue can read portions of process memory that may contain document content, heap metadata, or other sensitive runtime data.
Root Cause
The root cause is improper validation of input bounds during document parsing. Office reads structured content from a file without verifying that the requested offset or length stays within the allocated buffer. When a malformed structure is processed, the parser dereferences memory past the buffer end and returns that data to subsequent code paths.
Attack Vector
Exploitation requires local access and user interaction. The attacker delivers a crafted Office document to the target, typically through email, a file share, or a web download. When the victim opens the file in a vulnerable version of Office, the parser triggers the out-of-bounds read. Refer to the Microsoft Security Update CVE-2026-45485 advisory for product-specific details. No verified public proof-of-concept code is currently available.
Detection Methods for CVE-2026-45485
Indicators of Compromise
- Unexpected Office process crashes or memory access exceptions logged in the Windows Event Log when opening documents from external sources.
- Receipt of Office documents from untrusted senders containing malformed embedded structures or unusual binary content.
- Office processes spawning network connections shortly after opening documents that exhibit parsing anomalies.
Detection Strategies
- Monitor endpoint telemetry for winword.exe, excel.exe, and other Office binaries generating exception events or unusual memory reads.
- Inspect inbound email attachments and downloaded documents with sandboxed detonation to surface anomalous parsing behavior.
- Correlate Office process activity with subsequent suspicious behavior such as credential access or staging of exfiltration files.
Monitoring Recommendations
- Enable Microsoft Office Protected View and audit logging for documents originating from the internet or email.
- Track Office application version inventory to confirm coverage of the June 2026 security update.
- Alert on Office documents containing macros, embedded OLE objects, or non-standard file structures arriving from untrusted senders.
How to Mitigate CVE-2026-45485
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update CVE-2026-45485 advisory across all affected Office installations.
- Inventory endpoints running Microsoft Office and prioritize patching for users who routinely handle external documents.
- Reinforce user awareness on opening documents from unknown or untrusted sources.
Patch Information
Microsoft released the fix on June 9, 2026 as part of the standard security update cycle. Administrators should deploy the update through Microsoft Update, Windows Server Update Services (WSUS), Microsoft Intune, or other managed software distribution tooling. Validate patch installation using the build numbers documented in the Microsoft Security Update CVE-2026-45485 advisory.
Workarounds
- Enforce Protected View for files originating from the internet, email attachments, and unsafe locations.
- Block or quarantine Office document attachments from untrusted external senders at the mail gateway until patching is complete.
- Configure Attack Surface Reduction (ASR) rules to limit Office child process creation and code injection paths.
# Configuration example: enforce Protected View via Group Policy registry keys
reg add "HKCU\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableInternetFilesInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Microsoft\Office\16.0\Word\Security\ProtectedView" /v DisableAttachmentsInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\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.
