CVE-2026-44824: Microsoft Office Buffer Overflow Flaw

CVE-2026-44824 Overview

CVE-2026-44824 is a heap-based buffer overflow vulnerability in Microsoft Office that enables local code execution. The flaw is classified under [CWE-122] and requires user interaction to trigger. An attacker crafts a malicious Office document and convinces a user to open it. Successful exploitation runs arbitrary code in the context of the current user.

The vulnerability carries a CVSS 3.1 score of 7.8 with the vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. The EPSS score is 0.079% as of 2026-06-11. No public exploit code or CISA KEV listing has been recorded.

Critical Impact
Successful exploitation grants the attacker the ability to execute arbitrary code with the privileges of the current user, leading to full compromise of confidentiality, integrity, and availability on the affected host.

Affected Products

Microsoft Office (specific versions listed in the Microsoft Security Update CVE-2026-44824)

Discovery Timeline

2026-06-09 - CVE-2026-44824 published to NVD
2026-06-09 - Last updated in NVD database

Technical Details for CVE-2026-44824

Vulnerability Analysis

The vulnerability is a heap-based buffer overflow inside Microsoft Office document parsing routines. The flaw allows an attacker to write beyond the bounds of a heap-allocated buffer when Office processes a malformed document. The overwrite can corrupt adjacent heap metadata or function pointers used by Office during rendering. An attacker leverages this corruption to redirect execution into attacker-controlled memory.

Exploitation results in code execution under the security context of the user opening the document. The vulnerability does not cross a security boundary on its own. Attackers typically chain it with a privilege escalation flaw to gain SYSTEM access.

Root Cause

The root cause is improper bounds checking when Office allocates and writes data into a heap buffer during document parsing. The size of incoming structured data is not validated against the destination allocation. Specially crafted records inside an Office file trigger the over-write. The defect maps to [CWE-122] Heap-based Buffer Overflow.

Attack Vector

The attack vector is local with required user interaction. An attacker delivers a weaponized Office document through email, web download, or removable media. The victim opens the file in a vulnerable Office application. Office parses the malicious record, triggers the heap overflow, and runs the attacker's payload. No authentication is required to deliver the file.

No verified public proof-of-concept is available. Technical details are limited to the vendor advisory at the Microsoft Security Update CVE-2026-44824 page.

Detection Methods for CVE-2026-44824

Indicators of Compromise

Unexpected child processes spawned by winword.exe, excel.exe, or powerpnt.exe such as cmd.exe, powershell.exe, wscript.exe, or rundll32.exe.
Office applications writing executable files (.exe, .dll, .scr) to %TEMP%, %APPDATA%, or %PUBLIC% directories.
Office application crashes followed by anomalous network connections to unfamiliar external hosts.
Email attachments or downloads containing Office documents with embedded malformed binary records.

Detection Strategies

Hunt for process-tree anomalies where Office binaries parent script interpreters or living-off-the-land binaries.
Monitor for memory-protection violations and access-violation crashes in Office processes via Windows Error Reporting (Werfault.exe).
Apply YARA rules against documents in mail gateways to flag malformed structured-storage records and oversized stream sizes.

Monitoring Recommendations

Forward Sysmon Event IDs 1 (process create), 7 (image load), and 11 (file create) from endpoints running Office to a centralized analytics platform.
Alert on Office processes loading non-Microsoft-signed DLLs from user-writable paths.
Track outbound network connections initiated by Office processes immediately after document open events.

How to Mitigate CVE-2026-44824

Immediate Actions Required

Apply the security update referenced in the Microsoft Security Update CVE-2026-44824 advisory across all systems running Microsoft Office.
Enforce Protected View and Application Guard for Office for documents originating from the internet or email.
Block macro execution from files originating from the internet using Group Policy.

Patch Information

Microsoft has issued a security update through the Microsoft Update Guide. Administrators should deploy the patch via Windows Update, Microsoft Update Catalog, WSUS, or Intune. Confirm coverage on Click-to-Run and MSI-based Office installations. Reference the Microsoft Security Update CVE-2026-44824 for the exact build numbers per channel.

Workarounds

Open untrusted Office documents only in Protected View or in a sandboxed environment.
Deploy Attack Surface Reduction (ASR) rules that block Office applications from creating child processes and from injecting code into other processes.
Restrict opening of Office file formats received via email by routing attachments through a detonation sandbox prior to delivery.

bash

# Configuration example: enable ASR rules via PowerShell
Set-MpPreference -AttackSurfaceReductionRules_Ids `
  D4F940AB-401B-4EFC-AADC-AD5F3C50688A, `
  3B576869-A4EC-4529-8536-B80A7769E899, `
  75668C1F-73B5-4CF0-BB93-3ECF5CB7CC84 `
  -AttackSurfaceReductionRules_Actions Enabled,Enabled,Enabled