CVE-2024-49028: Microsoft Excel RCE Vulnerability

CVE-2024-49028 Overview

CVE-2024-49028 is a remote code execution vulnerability in Microsoft Excel disclosed by Microsoft in the November 2024 security update. The flaw stems from an out-of-bounds read condition tracked as [CWE-125] in Excel file parsing logic. An attacker who successfully exploits this issue can execute arbitrary code in the context of the current user.

Exploitation requires the victim to open a specially crafted Excel document, making phishing and social engineering the most likely delivery methods. The vulnerability affects Microsoft 365 Apps, Microsoft Excel 2016, Microsoft Office 2019, and Microsoft Office Long Term Servicing Channel 2021 and 2024 on Windows and macOS.

Critical Impact
Successful exploitation grants arbitrary code execution under the current user's privileges, enabling malware installation, data theft, and lateral movement.

Affected Products

Microsoft 365 Apps (Enterprise)
Microsoft Excel 2016 and Microsoft Office 2019
Microsoft Office Long Term Servicing Channel 2021 and 2024 (Windows and macOS)

Discovery Timeline

2024-11-12 - CVE-2024-49028 published to NVD as part of Microsoft's November 2024 Patch Tuesday
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-49028

Vulnerability Analysis

CVE-2024-49028 is an out-of-bounds read weakness in Microsoft Excel's document parsing routines. When Excel processes a malformed spreadsheet, the parser reads memory beyond the intended buffer boundary. Attackers can shape the crafted file to influence adjacent memory and steer execution flow.

The issue requires local user interaction, meaning the victim must open the attacker-supplied file. The scope remains unchanged, and confidentiality, integrity, and availability are each impacted at the highest level. Microsoft classifies the vulnerability as a remote code execution issue because the file itself is typically delivered from a remote source such as email or a shared link.

Root Cause

The root cause is improper bounds checking on structured data within an Excel document [CWE-125]. Malformed record sizes or offset fields cause Excel to read memory outside the allocated buffer. This condition can be chained with heap grooming to achieve code execution in the Excel process.

Attack Vector

The attack vector is local file open. An attacker crafts a malicious .xlsx, .xls, or related Office document and delivers it through phishing email, a shared drive, or a drive-by download. When a user opens the file, Excel parses the malformed structures and the out-of-bounds read triggers. No verified public proof-of-concept code is available for this CVE. See the Microsoft CVE-2024-49028 Advisory for vendor guidance.

Detection Methods for CVE-2024-49028

Indicators of Compromise

Excel processes (EXCEL.EXE) spawning unusual child processes such as cmd.exe, powershell.exe, wscript.exe, or rundll32.exe.
Unexpected outbound network connections initiated from Excel following the opening of an email attachment.
Office documents delivered from external senders that contain unusually large or malformed BIFF or OOXML records.

Detection Strategies

Hunt for anomalous parent-child process chains where EXCEL.EXE launches script interpreters or LOLBins.
Inspect email gateway telemetry for spreadsheet attachments from untrusted senders and detonate suspicious files in a sandbox.
Correlate Office child process events with subsequent file writes to user-writable directories or persistence locations.

Monitoring Recommendations

Enable Microsoft Defender Attack Surface Reduction rules that block Office applications from creating child processes.
Forward Office telemetry, Sysmon process creation events, and EDR logs to a centralized analytics platform for correlation.
Alert on Excel crashes with exception codes consistent with memory access violations, which may indicate exploitation attempts.

How to Mitigate CVE-2024-49028

Immediate Actions Required

Apply the November 2024 Microsoft security updates for Microsoft 365 Apps, Excel 2016, Office 2019, and Office LTSC 2021/2024 on both Windows and macOS.
Prioritize patching for users who regularly receive external spreadsheet attachments, such as finance and procurement teams.
Verify update deployment status across managed endpoints and remediate any hosts that failed to install the patch.

Patch Information

Microsoft released fixes for CVE-2024-49028 on November 12, 2024. Refer to the Microsoft CVE-2024-49028 Advisory for the specific build numbers for each affected channel and platform.

Workarounds

Open untrusted spreadsheets in Protected View and disable the option to exit Protected View automatically.
Configure Office File Block policy to prevent opening legacy binary Excel formats from Internet Zone sources.
Enable Attack Surface Reduction rule D4F940AB-401B-4EFC-AADC-AD5F3C50688A to block child process creation from Office applications.

bash

# Configuration example: enable ASR rule to block Office child processes
Set-MpPreference -AttackSurfaceReductionRules_Ids D4F940AB-401B-4EFC-AADC-AD5F3C50688A \
  -AttackSurfaceReductionRules_Actions Enabled