Outlook Vulnerability Allows Remote Execution of Arbitrary Code by Attackers

Microsoft confirmed a critical security vulnerability (CVE-2025-47176) in Microsoft Office Outlook, enabling attackers to execute arbitrary code.

Despite the “Remote Code Execution” title, the attack vector is local, requiring attackers to run code from a user’s own machine.

However, the potential impact remains high for organizations, as successful exploitation can compromise the confidentiality, integrity, and availability of data.

Technical Analysis of the Vulnerability

The CVE title refers to the outcome—executing arbitrary code—while the attack vector is local.

The vulnerability stems from a file handling issue within Outlook, typically triggered by special characters or path sequences like “‘…/…//’” in file or attachment names.

When Outlook parses these, an attacker with low privileges and local access can manipulate the process to execute arbitrary code.

Once an attacker gains low-privilege access to a workstation (e.g., via phishing), they can prepare a malicious file or use Outlook’s file handling mechanisms (like saving and opening attachments) to exploit this bug. Here’s a simplified example workflow:

1. Attacker gains access to a victim’s Outlook environment (typically by tricking a user to run or save files via social engineering).
2. The attacker injects a specially crafted file or triggers a path traversal, causing Outlook to parse malformed file names.
3. The vulnerable Outlook client executes attacker-controlled code with the victim’s user privileges.

A theoretical exploit might involve crafting a file or attachment with a path like:

text../../../../../evil.exe

or

text…/…//malicious.ps1

However, real-world exploitation often requires more context, such as embedding this inside an email attachment that Outlook parses improperly. No public PoC (Proof of Concept) scripts or tools are available as of this writing.

Mitigation and Patch Status

Microsoft has acknowledged the vulnerability but has not yet released a fix for Microsoft 365 for Office.

Customers should monitor the official Microsoft Security Response Center (MSRC) and the CVE page for updates.

1. Restrict Privileges: Limit local user privileges wherever possible.
2. Monitor File Handling: Use security tools to block execution of suspicious files from email attachments.
3. Stay Informed: Watch for official updates from Microsoft and patch promptly once updates are available.
4. Educate Users: Train employees to recognize phishing and suspicious attachments.

Security teams can monitor for unusual patterns in Outlook activity or file parsing. For example, using PowerShell, a script could scan event logs for suspicious file paths:

powershellGet-WinEvent -LogName "Microsoft Office Alerts" | Where-Object {
    $_.Message -match "..[/\]{2,}|…/…/"
}

This will help detect attempts to exploit path traversal or unusual file parsing.

The CVE-2025-47176 vulnerability in Microsoft Outlook is a reminder of the persistent threat that simple bugs in complex applications can pose.

Although not remotely exploitable in the sense of being triggered over the network without any user action, it is a local code execution bug that could be a stepping stone for attackers already present on a system.

Organizations must remain vigilant and ready to apply patches as soon as they are available.

Continuous education and robust security monitoring are essential components in mitigating such threats.

Microsoft acknowledges Shmuel Uzan, Michael Gorelik, and Arnold Osipov from Morphisec for reporting this vulnerability through coordinated disclosure.

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