CVE-2024-49030: Microsoft Excel RCE Vulnerability

CVE-2024-49030 Overview

CVE-2024-49030 is a remote code execution vulnerability in Microsoft Excel that stems from a heap-based buffer overflow [CWE-122]. Successful exploitation allows an attacker to execute arbitrary code in the context of the current user. The flaw affects multiple Microsoft Office products, including Microsoft 365 Apps, Excel 2016, Office 2019, and Office Long Term Servicing Channel 2021 and 2024 for both Windows and macOS. Exploitation requires the victim to open a crafted Excel file, making phishing and social engineering the primary delivery methods. Microsoft published the advisory on November 12, 2024 as part of the monthly security update cycle.

Critical Impact
An attacker who convinces a user to open a malicious Excel document can achieve arbitrary code execution with the privileges of the logged-on user, resulting in full compromise of confidentiality, integrity, and availability on the host.

Affected Products

Microsoft 365 Apps for 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-2024-49030 published to NVD alongside Microsoft's security advisory
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-49030

Vulnerability Analysis

CVE-2024-49030 is a heap-based buffer overflow within Microsoft Excel's document parsing logic. When Excel processes a specially crafted spreadsheet, memory allocated on the heap is written beyond its intended bounds. An attacker who controls the overflowed data can corrupt adjacent heap structures, hijack control flow, and execute arbitrary code inside the EXCEL.EXE process. The resulting code runs with the privileges of the current user, providing a foothold that can be extended through follow-on tooling or credential theft.

The attack vector is local because the malicious payload must be delivered as a file and opened by a user. However, delivery over email, cloud shares, or web downloads makes real-world exploitation practical. User interaction is required, so protected view and Mark-of-the-Web indicators are important defensive controls.

Root Cause

The root cause is improper validation of size or offset fields inside an embedded Excel structure, which allows a copy operation to exceed the size of a heap-allocated buffer. Microsoft classifies the defect under [CWE-122: Heap-based Buffer Overflow]. Because the underlying allocator metadata and adjacent objects can be manipulated, the condition is exploitable for arbitrary code execution rather than a simple crash.

Attack Vector

An attacker crafts a malicious .xls, .xlsx, or related Office document containing the malformed structure. The file is delivered through phishing email, malicious link, or shared document repository. When the victim opens the document and bypasses Protected View, the parser triggers the overflow and the embedded shellcode or ROP chain executes. No verified public proof-of-concept is available at this time, and the vulnerability is not listed on the CISA Known Exploited Vulnerabilities catalog.

See the Microsoft Vulnerability Advisory for vendor guidance.

Detection Methods for CVE-2024-49030

Indicators of Compromise

Unexpected child processes spawned by EXCEL.EXE, such as cmd.exe, powershell.exe, wscript.exe, rundll32.exe, or mshta.exe.
Excel writing executables, scripts, or scheduled task artifacts to %TEMP%, %APPDATA%, or %PUBLIC%.
Outbound network connections initiated by EXCEL.EXE to previously unseen domains or IP addresses immediately after document open.
Office documents arriving from external senders that contain unusually large or malformed BIFF/OOXML records.

Detection Strategies

Hunt for process ancestry chains where EXCEL.EXE is the parent of scripting or living-off-the-land binaries.
Alert on Office applications loading unsigned DLLs or performing memory allocations with RWX permissions.
Correlate email gateway telemetry for Excel attachments from untrusted senders with subsequent endpoint anomalies on the recipient's host.

Monitoring Recommendations

Enable Microsoft Defender Attack Surface Reduction (ASR) rules that block child process creation from Office applications and audit blocked events.
Forward Sysmon Event IDs 1, 7, 11, and 3 from workstations running Office to a centralized SIEM for behavioral analytics.
Track patch compliance for EXCEL.EXE file versions and flag hosts that fall behind the current Microsoft security baseline.

How to Mitigate CVE-2024-49030

Immediate Actions Required

Apply the November 2024 Microsoft security updates to all affected Office and Microsoft 365 Apps installations without delay.
Prioritize patching for endpoints belonging to executives, finance staff, and other high-value phishing targets.
Verify that Protected View and Mark-of-the-Web enforcement remain enabled for documents originating from the internet or email.

Patch Information

Microsoft released fixes through its standard update channels. Administrators should reference the Microsoft Security Response Center advisory for CVE-2024-49030 to identify the specific KB articles and build numbers for each affected channel, including Microsoft 365 Apps, Office 2019, Office LTSC 2021, and Office LTSC 2024 on Windows and macOS.

Workarounds

Enforce Office Attack Surface Reduction rules to block child process creation and Win32 API calls from Office macros.
Disable execution of macros from files originating on the internet using Group Policy or Intune configuration profiles.
Route inbound Excel attachments through a sandbox or content disarm and reconstruction (CDR) tool until patching is verified.

bash

# Example: enforce ASR rule blocking child processes from Office apps
Set-MpPreference -AttackSurfaceReductionRules_Ids `
  D4F940AB-401B-4EFC-AADC-AD5F3C50688A `
  -AttackSurfaceReductionRules_Actions Enabled

# Verify Excel build version post-patch
(Get-Item "$env:ProgramFiles\Microsoft Office\root\Office16\EXCEL.EXE").VersionInfo