CVE-2025-53741 Overview
CVE-2025-53741 is a heap-based buffer overflow vulnerability in Microsoft Office Excel that allows an unauthorized attacker to execute arbitrary code locally. The flaw affects multiple supported Excel and Office distributions, including Microsoft 365 Apps, Excel 2016, Office 2019, the Office Long Term Servicing Channel (LTSC) 2021 and 2024, and Office Online Server. Exploitation requires user interaction, typically by opening a specially crafted Excel document. Microsoft classified the issue under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write).
Critical Impact
Successful exploitation results in arbitrary code execution in the context of the logged-in user, enabling malware deployment, data theft, and lateral movement from a single crafted spreadsheet.
Affected Products
- Microsoft 365 Apps (Enterprise, x86 and x64)
- Microsoft Excel 2016, Office 2019, Office LTSC 2021 and 2024 (including macOS builds of LTSC)
- Microsoft Office Online Server
Discovery Timeline
- 2025-08-12 - CVE-2025-53741 published to NVD and addressed by Microsoft
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-53741
Vulnerability Analysis
The vulnerability is a heap-based buffer overflow in the Excel file parsing logic. When Excel processes a malformed spreadsheet, the code writes data past the bounds of a heap-allocated buffer, corrupting adjacent memory structures. An attacker who controls the overflowing bytes can overwrite function pointers, vtables, or other heap metadata to redirect execution. The issue is reachable through any code path that opens an Excel document, including the Outlook Preview Pane when configured to render Office content. Microsoft mapped the issue to CWE-122 and CWE-787.
Root Cause
The root cause is improper validation of length or offset values within an Excel record before data is copied into a fixed-size heap allocation. Without bounds enforcement, attacker-controlled fields produce an out-of-bounds write on the heap. This is a recurring class of defect in legacy Office binary file format parsers.
Attack Vector
The attack vector is local and requires user interaction. An attacker delivers a weaponized .xls, .xlsx, or related Excel document through email, a phishing link, a shared drive, or a compromised website. When the victim opens the file in a vulnerable Excel build, the parser triggers the overflow and runs attacker-supplied shellcode under the user's privileges. No authentication to the target system is required from the attacker beyond convincing the user to open the file.
No public proof-of-concept code is available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. EPSS data published on 2026-06-23 reflects a low near-term exploitation probability.
Detection Methods for CVE-2025-53741
Indicators of Compromise
- Excel processes (EXCEL.EXE) spawning unexpected child processes such as cmd.exe, powershell.exe, rundll32.exe, regsvr32.exe, or mshta.exe.
- Excel writing executable files, scripts, or DLLs to user-writable paths such as %TEMP%, %APPDATA%, or %LOCALAPPDATA%.
- Unusual outbound network connections initiated by EXCEL.EXE to non-Microsoft destinations shortly after a document is opened.
- Crashes of EXCEL.EXE with heap corruption signatures in Windows Error Reporting (WER) logs.
Detection Strategies
- Hunt for Office applications acting as parent processes for LOLBins and script interpreters, a behavior consistent with Office document exploitation.
- Inspect inbound Excel attachments with sandbox detonation to identify malformed records or shellcode patterns prior to user delivery.
- Correlate document open events with subsequent process creation and file write telemetry to surface exploitation chains.
Monitoring Recommendations
- Enable and forward Microsoft Defender ASR rule events, especially "Block all Office applications from creating child processes," to your SIEM.
- Collect Sysmon EventID 1 (process creation), EventID 7 (image load), and EventID 11 (file create) for the Office process tree.
- Monitor email gateway telemetry for spreadsheets originating from new external senders with macro or external link content.
How to Mitigate CVE-2025-53741
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update Guide for CVE-2025-53741 across all affected Excel and Office channels.
- Inventory endpoints running Microsoft 365 Apps, Excel 2016, Office 2019, Office LTSC 2021/2024, and Office Online Server, and confirm the patched build is installed.
- Enforce Protected View and Block Macros from the Internet via Group Policy for all Office users.
Patch Information
Microsoft has issued patches for all supported channels listed in the advisory. Administrators should consult the Microsoft Security Update Guide for CVE-2025-53741 for the exact build numbers per product and validate deployment through update compliance reporting.
Workarounds
- Disable the Outlook Preview Pane to prevent rendering of attached spreadsheets without explicit user action.
- Enforce Microsoft Defender Attack Surface Reduction (ASR) rules to block Office applications from creating child processes and from injecting code into other processes.
- Restrict opening of Excel files from untrusted sources using File Block policy and require Protected View for files from the internet and unsafe locations.
# Configuration example - enable ASR rule blocking Office child process creation
Set-MpPreference -AttackSurfaceReductionRules_Ids D4F940AB-401B-4EFC-AADC-AD5F3C50688A `
-AttackSurfaceReductionRules_Actions Enabled
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
