CVE-2025-62202: Microsoft 365 Apps Info Disclosure Flaw

CVE-2025-62202 Overview

CVE-2025-62202 is an out-of-bounds read vulnerability in Microsoft Office Excel that allows an unauthorized attacker to disclose information locally. The flaw is categorized under [CWE-125] and affects multiple Microsoft Office product lines, including Microsoft 365 Apps, Excel 2016, Office 2019, Office LTSC 2021 and 2024, and Office Online Server. Exploitation requires user interaction, typically by opening a maliciously crafted Excel document. Successful exploitation can leak sensitive memory contents from the Excel process, which attackers may use to bypass mitigations such as Address Space Layout Randomization (ASLR) or to chain with other vulnerabilities.

Critical Impact

An attacker who tricks a user into opening a crafted Excel file can read out-of-bounds memory, exposing sensitive process data and potentially aiding further exploitation.

Affected Products

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

Discovery Timeline

• 2025-11-11 - CVE-2025-62202 published to NVD
• 2025-11-17 - Last updated in NVD database

Technical Details for CVE-2025-62202

Vulnerability Analysis

The vulnerability is an out-of-bounds read [CWE-125] in the Excel file parsing logic. When Excel processes a specifically crafted spreadsheet, the application reads memory beyond the bounds of an allocated buffer. The leaked data resides in the address space of the Excel process and may include heap metadata, pointers, or fragments of other documents loaded in the same session.

The attack vector is local and requires user interaction. An attacker delivers a malicious .xls, .xlsx, or related Office file through email, a shared drive, or a download. The user must open the file in a vulnerable Excel build for the parser to trigger the read. No elevated privileges are required on the target system.

The primary impact is information disclosure. While the flaw does not directly grant code execution, leaked memory addresses can defeat ASLR and serve as a building block for chained exploits against companion Office vulnerabilities patched in the same release cycle.

Root Cause

The root cause is missing or insufficient bounds validation when Excel parses structured fields inside a workbook. A malformed record length or index causes the parser to read past the end of a buffer, returning adjacent process memory to attacker-controlled structures.

Attack Vector

An attacker crafts a malicious Excel document containing malformed record structures. The file is delivered through phishing, watering-hole websites, or shared file repositories. When the victim opens the file, the parsing routine performs the out-of-bounds read, and the leaked data can be exfiltrated through embedded objects, formula channels, or staged follow-on payloads. Detailed technical analysis is not publicly available. See the Microsoft Security Update CVE-2025-62202 advisory for vendor-supplied details.

Detection Methods for CVE-2025-62202

Indicators of Compromise

• Inbound email attachments containing Excel files from unverified senders, especially with macro-enabled extensions such as .xlsm or unusual binary .xls formats.
• Crash or anomalous termination of EXCEL.EXE shortly after opening a document, recorded in Windows Event Log under Application Error events.
• Outbound network connections initiated by EXCEL.EXE immediately following document open, indicating possible data exfiltration of leaked memory.

Detection Strategies

• Monitor child process creation under EXCEL.EXE for unusual binaries such as powershell.exe, cmd.exe, wscript.exe, or mshta.exe.
• Inspect Office telemetry for documents originating from the internet zone (Mark-of-the-Web) being opened by users in sensitive roles.
• Apply YARA or content-inspection rules on mail gateways to flag Excel files with malformed record structures or suspicious embedded OLE objects.

Monitoring Recommendations

• Centralize Office application logs and Windows Defender Application Guard telemetry in a SIEM for correlation with phishing campaign indicators.
• Track Office version inventory across managed endpoints to identify hosts still running unpatched Excel builds.
• Enable Attack Surface Reduction (ASR) rules that block Office applications from creating child processes and writing to executable content.

How to Mitigate CVE-2025-62202

Immediate Actions Required

• Apply the November 2025 Microsoft security updates referenced in the Microsoft Security Update CVE-2025-62202 advisory to all affected Office installations.
• Prioritize patching workstations used by high-value users such as executives, finance staff, and administrators who are common phishing targets.
• Verify that Microsoft 365 Apps clients are configured for the Current Channel or Monthly Enterprise Channel and have received the latest cumulative update.

Patch Information

Microsoft released fixes for CVE-2025-62202 as part of its November 2025 Patch Tuesday release. Administrators should consult the Microsoft Security Update CVE-2025-62202 page for specific build numbers covering Microsoft 365 Apps, Excel 2016, Office 2019, Office LTSC 2021, Office LTSC 2024, and Office Online Server on both Windows and macOS.

Workarounds

• Enforce Protected View for all files originating from the internet and from Outlook attachments through Group Policy.
• Block or quarantine Excel attachments from untrusted external senders at the mail gateway until patches are deployed.
• Enable Microsoft Defender Attack Surface Reduction rules to prevent Office applications from creating executable child processes.

# Configuration example: enforce Protected View via Group Policy registry keys
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Excel\Security\ProtectedView" /v DisableInternetFilesInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Excel\Security\ProtectedView" /v DisableAttachmentsInPV /t REG_DWORD /d 0 /f
reg add "HKCU\Software\Policies\Microsoft\Office\16.0\Excel\Security\ProtectedView" /v DisableUnsafeLocationsInPV /t REG_DWORD /d 0 /f