CVE-2026-26113: Microsoft Office RCE Vulnerability

CVE-2026-26113 Overview

CVE-2026-26113 is an untrusted pointer dereference vulnerability in Microsoft Office that allows an unauthorized attacker to execute code locally. This memory corruption flaw occurs when the application improperly handles pointer values from untrusted sources, enabling attackers to manipulate program execution flow and potentially achieve arbitrary code execution on affected systems.

Critical Impact

This vulnerability enables local code execution without requiring any user privileges, potentially allowing attackers to compromise systems running vulnerable Microsoft Office installations and gain full control over the affected host.

Affected Products

• Microsoft Office (specific versions to be confirmed via vendor advisory)

Discovery Timeline

• 2026-03-10 - CVE-2026-26113 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2026-26113

Vulnerability Analysis

This vulnerability is classified under CWE-822 (Untrusted Pointer Dereference), a serious memory corruption issue that occurs when an application dereferences a pointer that has been obtained from an untrusted source without proper validation. In the context of Microsoft Office, this flaw allows an attacker operating locally to manipulate memory operations, bypassing normal security controls and executing arbitrary code.

The local attack vector means an attacker would need either physical access to the target system or the ability to execute code through another mechanism (such as social engineering a user to open a malicious document). Once exploited, the vulnerability can lead to complete compromise of confidentiality, integrity, and availability on the affected system.

Root Cause

The root cause of CVE-2026-26113 lies in improper validation of pointer values before dereferencing within Microsoft Office components. When the application processes certain data structures, it fails to verify that pointer values originate from trusted memory regions. This allows an attacker to inject malicious pointer values that, when dereferenced, redirect program execution to attacker-controlled memory locations.

Untrusted pointer dereference vulnerabilities typically arise from:

• Accepting pointer values from user-controlled input without validation
• Failure to implement proper bounds checking on memory operations
• Missing integrity checks on data structures containing pointer values

Attack Vector

The attack vector for this vulnerability is local, requiring the attacker to have some level of access to the target system. Exploitation typically involves:

1. Crafting a malicious document - An attacker creates a specially crafted Office document containing malicious data structures with manipulated pointer values
2. Delivery mechanism - The malicious document is delivered to the victim through email, file sharing, or other means
3. Triggering the vulnerability - When the victim opens the document, Office processes the malicious data, dereferencing the untrusted pointer
4. Code execution - The dereferenced pointer redirects execution to attacker-controlled memory, enabling arbitrary code execution with the privileges of the Office application

The vulnerability does not require user interaction beyond opening the malicious document, and no special privileges are needed to exploit it.

Detection Methods for CVE-2026-26113

Indicators of Compromise

• Unexpected crashes or abnormal termination of Microsoft Office applications
• Office processes spawning unusual child processes or executing unexpected system commands
• Memory access violations or exception events logged in Windows Event Viewer related to Office components
• Suspicious Office document files with unusual internal structures or embedded objects

Detection Strategies

• Implement application whitelisting to prevent unauthorized code execution from Office processes
• Deploy endpoint detection and response (EDR) solutions capable of monitoring Office process behavior for anomalous memory operations
• Enable Windows Defender Exploit Guard with memory protection features such as Control Flow Guard (CFG) and Arbitrary Code Guard (ACG)
• Monitor for Office applications making unexpected API calls or accessing sensitive system resources

Monitoring Recommendations

• Configure centralized logging for Microsoft Office application events and Windows Security events
• Implement file integrity monitoring on Office installation directories to detect tampering
• Deploy network monitoring to identify suspicious document transfers that may contain exploit payloads
• Regularly review endpoint telemetry for Office-related process anomalies

How to Mitigate CVE-2026-26113

Immediate Actions Required

• Apply the latest security updates from Microsoft as soon as they become available
• Enable Protected View in Microsoft Office to open documents from untrusted sources in a sandboxed environment
• Implement application-level controls to restrict Office macro execution and ActiveX content
• Educate users about the risks of opening documents from untrusted or unknown sources

Patch Information

Microsoft has released a security update addressing this vulnerability. Detailed patch information is available through the Microsoft Security Update Guide for CVE-2026-26113. Organizations should prioritize deploying this update across all affected systems through their standard patch management processes.

Workarounds

• Enable Protected View for all Office documents by navigating to File > Options > Trust Center > Trust Center Settings > Protected View
• Configure Office to block macros from running in documents downloaded from the internet
• Use Microsoft's Attack Surface Reduction (ASR) rules to block Office applications from creating child processes or injecting code into other processes
• Consider deploying Microsoft Office in a virtualized or containerized environment to limit the impact of potential exploitation

# Enable ASR rules for Office protection via PowerShell
Set-MpPreference -AttackSurfaceReductionRules_Ids BE9BA2D9-53EA-4CDC-84E5-9B1EEEE46550 -AttackSurfaceReductionRules_Actions Enabled
Set-MpPreference -AttackSurfaceReductionRules_Ids D4F940AB-401B-4EFC-AADC-AD5F3C50688A -AttackSurfaceReductionRules_Actions Enabled