CVE-2024-43465: Microsoft Excel Privilege Escalation

CVE-2024-43465 Overview

CVE-2024-43465 is an elevation of privilege vulnerability in Microsoft Excel caused by a use-after-free memory condition [CWE-416]. An attacker who successfully exploits this flaw can gain higher privileges on the affected system after a user opens a specially crafted Excel file. The vulnerability affects multiple supported Office products, including Microsoft 365 Apps, Excel 2016, Office 2019, Office LTSC 2021 (Windows and macOS), and Office Online Server. Microsoft published the advisory on September 10, 2024 as part of its Patch Tuesday release cycle.

Critical Impact
Successful exploitation grants elevated privileges on the target host with high impact to confidentiality, integrity, and availability.

Affected Products

Microsoft 365 Apps (Enterprise, x86 and x64)
Microsoft Excel 2016, Microsoft Office 2019
Microsoft Office LTSC 2021 (Windows and macOS), Microsoft Office Online Server

Discovery Timeline

2024-09-10 - Microsoft releases security patch addressing CVE-2024-43465
2024-09-10 - CVE-2024-43465 published to NVD
2026-08-10 - Last updated in NVD database

Technical Details for CVE-2024-43465

Vulnerability Analysis

CVE-2024-43465 is a use-after-free vulnerability in Microsoft Excel. The flaw is triggered when Excel processes a specially crafted spreadsheet file that manipulates internal object lifecycles. When the application frees a memory region but continues to hold a stale reference, an attacker can reclaim that memory and influence subsequent operations that dereference the freed pointer.

Exploitation requires local access and user interaction. A victim must open the malicious document, typically delivered via phishing or a compromised file share. Once opened, the attacker can execute code in the context of the affected process and elevate privileges within the current user session.

Microsoft classifies the issue as elevation of privilege rather than remote code execution because the initial code execution occurs at the invoking user's privilege level, and the attacker leverages the freed-object primitive to escalate beyond the Office sandbox or protected view boundaries.

Root Cause

The root cause is improper memory management in Excel's object handling code. An object is released, but a reference to it remains reachable. Subsequent operations dereference the dangling pointer, allowing the attacker to control freed memory contents. This condition maps to [CWE-416] Use After Free.

Attack Vector

The attack vector is local. An attacker crafts a malicious .xlsx, .xlsm, or related Excel document containing structures that trigger the vulnerable code path. Delivery methods include email attachments, links to attacker-controlled file shares, and drive-by download scenarios. User interaction is required because the victim must open the file. Protected View may reduce but does not eliminate exposure if the user chooses to enable editing.

No public proof-of-concept code is available for this vulnerability at the time of writing. See the Microsoft Security Update CVE-2024-43465 advisory for authoritative technical details.

Detection Methods for CVE-2024-43465

Indicators of Compromise

Unexpected Excel process crashes or WerFault.exe events referencing EXCEL.EXE shortly after a document is opened.
Child processes spawned by EXCEL.EXE such as cmd.exe, powershell.exe, rundll32.exe, or mshta.exe.
Outbound network connections initiated by Excel to previously unseen domains or IP addresses.
Creation of executables, DLLs, or scripts in %APPDATA%, %TEMP%, or user profile directories immediately after document open events.

Detection Strategies

Hunt for Office applications loading unusual modules or spawning scripting interpreters, a common post-exploitation pattern for Office memory corruption bugs.
Correlate email or web download telemetry with subsequent Excel process anomalies to identify weaponized document delivery.
Inspect Excel files with embedded objects, unusual OLE streams, or malformed record structures using static analysis tooling.

Monitoring Recommendations

Enable and forward Microsoft Defender Application Guard, AMSI, and Windows Event logs from endpoints running Office.
Monitor Sysmon Event ID 1 (process creation) and Event ID 11 (file create) with a parent process filter on EXCEL.EXE.
Alert on any privilege token elevation events originating from Office application sessions.

How to Mitigate CVE-2024-43465

Immediate Actions Required

Apply the September 2024 Microsoft security updates to all affected Excel, Office, and Microsoft 365 Apps installations.
Prioritize patching for endpoints belonging to high-value users such as administrators, finance staff, and executives.
Verify Click-to-Run channels are updated by running OfficeC2RClient.exe /update user and confirming the build number reflects the September 2024 release.

Patch Information

Microsoft addressed CVE-2024-43465 in the September 10, 2024 Patch Tuesday release. Administrators should consult the Microsoft Security Update CVE-2024-43465 advisory for the specific update packages and build numbers corresponding to each affected product, including Microsoft 365 Apps, Office 2019, Office LTSC 2021, and Office Online Server.

Workarounds

Enforce Protected View and Office Application Guard for documents originating from the internet or email attachments.
Configure Attack Surface Reduction (ASR) rules to block Office applications from creating child processes and from injecting into other processes.
Restrict macro execution for files from the internet using Group Policy settings for Microsoft Office trust center configuration.
Train users to avoid enabling editing on unsolicited Excel documents until systems are patched.

bash

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