CVE-2026-64910: Microsoft Office RCE Vulnerability

CVE-2026-64910 Overview

CVE-2026-64910 is an untrusted pointer dereference vulnerability in Microsoft Office that allows an unauthorized attacker to execute code locally. The flaw is categorized under [CWE-822] (Untrusted Pointer Dereference) and requires user interaction to trigger, typically through opening a crafted Office document. Successful exploitation grants the attacker code execution in the context of the current user, compromising confidentiality, integrity, and availability on the affected host.

Critical Impact
An attacker who successfully exploits CVE-2026-64910 can execute arbitrary code on the target system by convincing a user to open a malicious Office file, leading to full compromise of the user session.

Affected Products

Microsoft Office (see the Microsoft CVE-2026-64910 Advisory for the current list of affected builds)
Office desktop applications processing untrusted document content
Systems where users open Office files from untrusted sources

Discovery Timeline

2026-08-11 - CVE-2026-64910 published to NVD
2026-08-12 - Last updated in NVD database

Technical Details for CVE-2026-64910

Vulnerability Analysis

CVE-2026-64910 is an untrusted pointer dereference weakness in Microsoft Office document parsing. The application dereferences a pointer whose value is influenced by attacker-controlled data in a specially crafted document. When the file is opened, Office reads structured content that supplies or influences a pointer value used in subsequent memory operations.

Because the pointer is not validated before use, the process reads or writes memory at an attacker-influenced address. This gives the attacker a primitive that can be shaped into arbitrary code execution within the Office process. The vulnerability requires local access and user interaction, but no prior authentication to the target system.

Root Cause

The root cause is missing validation of a pointer value that originates from untrusted input inside an Office document [CWE-822]. Office trusts the deserialized pointer as if it referred to a legitimate object, then dereferences it during normal document processing. Attackers who understand the affected data structure can craft input that steers the pointer to memory they control, enabling reliable exploitation.

Attack Vector

Exploitation is local and requires user interaction. An attacker delivers a weaponized Office document through phishing email, a shared drive, a chat platform, or a compromised web download. When a victim opens the file, Office parses the embedded structure containing the malicious pointer and dereferences it, transferring control to attacker-supplied logic.

No network access to the victim is required beyond the initial delivery of the file. Because execution runs under the current user's privileges, the attacker inherits access to that user's files, credentials, and network resources. Refer to the Microsoft CVE-2026-64910 Advisory for detailed product and build information.

Detection Methods for CVE-2026-64910

Indicators of Compromise

Office applications (WINWORD.EXE, EXCEL.EXE, POWERPNT.EXE) spawning unexpected child processes such as cmd.exe, powershell.exe, rundll32.exe, or mshta.exe.
Office processes making outbound network connections shortly after opening a document from an untrusted source.
Crashes or unusual memory access violations in Office processes correlated with document open events.
New persistence artifacts (scheduled tasks, Run keys, startup files) created in the same user session that opened an attachment.

Detection Strategies

Hunt for Office parent processes launching script interpreters or LOLBins immediately after a file open event.
Correlate email or web download telemetry with subsequent Office document opens to identify suspicious delivery chains.
Monitor for Office processes loading unsigned or unusual DLLs from user-writable paths.

Monitoring Recommendations

Ingest endpoint process, file, and network telemetry into a centralized data lake for cross-source correlation.
Enable Microsoft Office telemetry and Windows Defender Application Guard logs where available.
Alert on Office process crashes accompanied by exception codes consistent with pointer dereference faults (for example, 0xC0000005).

How to Mitigate CVE-2026-64910

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft CVE-2026-64910 Advisory to all Office installations.
Prioritize patching for users who routinely open documents from external senders, such as finance, HR, and executive staff.
Verify Protected View and Office Macro policies remain enforced across the estate until patching is complete.

Patch Information

Microsoft has published guidance and updates for CVE-2026-64910 through the Microsoft Security Response Center. Administrators should consult the Microsoft CVE-2026-64910 Advisory for the specific KB numbers, build versions, and channel-specific updates that address the vulnerability, then deploy through Windows Update, Microsoft Update, or managed update tooling.

Workarounds

Enforce Office Protected View for files from the internet, email attachments, and unsafe locations.
Use Attack Surface Reduction (ASR) rules to block Office applications from creating child processes and injecting into other processes.
Restrict opening of Office documents from untrusted origins through group policy and mail gateway controls.
Deliver targeted user awareness training on unsolicited Office attachments and enable-content prompts.

bash

# Example: enable Attack Surface Reduction rule to block Office child processes
# Rule GUID: D4F940AB-401B-4EFC-AADC-AD5F3C50688A (Block Office apps from creating child processes)
Set-MpPreference -AttackSurfaceReductionRules_Ids D4F940AB-401B-4EFC-AADC-AD5F3C50688A `
                 -AttackSurfaceReductionRules_Actions Enabled