CVE-2025-24081: Microsoft 365 Apps Use-After-Free Flaw

CVE-2025-24081 Overview

CVE-2025-24081 is a use-after-free vulnerability in Microsoft Office Excel that allows an unauthorized attacker to execute code locally. The flaw, categorized under [CWE-416], affects multiple Microsoft Office products including Microsoft 365 Apps, Excel 2016, Office 2019, Office LTSC 2021, Office LTSC 2024, and Office Online Server. Exploitation requires user interaction, typically achieved by convincing a victim to open a crafted Excel document. Successful exploitation yields code execution in the context of the current user, enabling attackers to install programs, modify data, or create new accounts with user rights.

Critical Impact
A crafted Excel file can trigger arbitrary code execution on the victim's machine, compromising confidentiality, integrity, and availability of the host.

Affected Products

Microsoft 365 Apps (x64 and x86, Enterprise)
Microsoft Excel 2016, Microsoft Office 2019
Microsoft Office LTSC 2021 and 2024 (Windows and macOS), Microsoft Office Online Server

Discovery Timeline

2025-03-11 - CVE-2025-24081 published to the National Vulnerability Database
2025-07-02 - Last updated in the NVD database

Technical Details for CVE-2025-24081

Vulnerability Analysis

The vulnerability is a use-after-free condition in Microsoft Office Excel. Use-after-free flaws occur when a program continues to reference memory after it has been freed, allowing an attacker to influence the contents of the reclaimed allocation and hijack execution flow. In Excel, this class of bug is typically triggered through malformed spreadsheet structures, embedded objects, or specific cell or formula constructs that cause the parser to release an object while a dangling pointer is still in use.

Exploitation requires the target to open a crafted .xlsx, .xls, or similar Excel-supported file. Because the attack vector is local with user interaction, threat actors commonly deliver the payload through phishing emails, drive-by downloads, or shared cloud storage links. Once the document is opened, the attacker gains code execution under the privileges of the logged-in user.

Root Cause

The root cause is improper object lifetime management within Excel's document parsing logic. A specific code path frees an internal object but retains a pointer that is later dereferenced. An attacker who controls the freed allocation can stage controlled data at that address, achieving an arbitrary read, write, or function pointer redirection that leads to code execution.

Attack Vector

The attack vector is local and requires user interaction. An attacker crafts a malicious Excel document and delivers it through standard social engineering channels. When the victim opens the file, Excel parses the malformed content, triggers the use-after-free condition, and executes attacker-supplied code. No elevated privileges are required prior to exploitation, and the attacker inherits the rights of the current user.

No public proof-of-concept exploit and no exploitation in the wild have been reported. Refer to the Microsoft Security Update Guide for CVE-2025-24081 for vendor technical details.

Detection Methods for CVE-2025-24081

Indicators of Compromise

Excel processes (EXCEL.EXE) spawning unusual child processes such as cmd.exe, powershell.exe, wscript.exe, or rundll32.exe.
Excel writing executable content to %TEMP%, %APPDATA%, or other user-writable directories.
Outbound network connections initiated directly from EXCEL.EXE to uncategorized or newly registered domains.
Crash events for Office processes referencing access violations in heap-allocated objects.

Detection Strategies

Hunt for parent-child process relationships where Excel launches script interpreters or living-off-the-land binaries (LOLBins).
Inspect inbound email attachments and shared documents for Excel files with embedded objects, macros, or unusual OLE streams.
Correlate Office telemetry with endpoint memory events to identify potential use-after-free exploitation patterns such as repeated heap spray allocations.

Monitoring Recommendations

Enable and forward Microsoft Office telemetry, Windows Sysmon process creation, and image load events to a centralized analytics platform.
Monitor for Excel-initiated DNS lookups and HTTP/S connections that deviate from baseline behavior.
Track Office application crashes via Windows Error Reporting (WER) to surface exploitation attempts that fail.

How to Mitigate CVE-2025-24081

Immediate Actions Required

Apply the Microsoft security updates referenced in the Microsoft Security Update Guide for CVE-2025-24081 to all affected Office installations.
Inventory endpoints running Microsoft 365 Apps, Excel 2016, Office 2019, and Office LTSC 2021/2024 to confirm patch coverage.
Reinforce user awareness on opening Excel attachments from untrusted or unexpected senders.

Patch Information

Microsoft has released security updates addressing CVE-2025-24081 across all affected channels. Administrators should deploy the latest cumulative updates through Microsoft Update, Windows Server Update Services (WSUS), Microsoft Intune, or the Microsoft 365 Apps update channels. macOS users of Office LTSC 2021 and 2024 should install the corresponding updates from Microsoft AutoUpdate.

Workarounds

Enable Protected View and Office Application Guard so untrusted Excel files open in an isolated container.
Block macros in files originating from the internet via the Block macros from running in Office files from the Internet Group Policy.
Use Attack Surface Reduction (ASR) rules to prevent Office applications from creating child processes and from injecting code into other processes.

bash

# Configuration example: enable Microsoft Defender ASR rules via PowerShell
# Block Office applications from creating child processes
Set-MpPreference -AttackSurfaceReductionRules_Ids D4F940AB-401B-4EFC-AADC-AD5F3C50688A `
                 -AttackSurfaceReductionRules_Actions Enabled

# Block Office applications from injecting code into other processes
Add-MpPreference -AttackSurfaceReductionRules_Ids 75668C1F-73B5-4CF0-BB93-3ECF5CB7CC84 `
                 -AttackSurfaceReductionRules_Actions Enabled

# Block executable content from email client and webmail
Add-MpPreference -AttackSurfaceReductionRules_Ids BE9BA2D9-53EA-4CDC-84E5-9B1EEEE46550 `
                 -AttackSurfaceReductionRules_Actions Enabled