Critical Windows OLE Zero-Click Vulnerability Let Attacker to Execute Arbitrary Code

A critical security flaw, identified as CVE-2025-21298, has been disclosed in Microsoft’s Windows Object Linking and Embedding (OLE) technology. 

This zero-click vulnerability, which carries a CVSS score of 9.8, allows attackers to execute arbitrary code remotely by exploiting Microsoft Outlook and other applications. 

The flaw has raised alarms across the cybersecurity community due to its severity and ease of exploitation. CVE-2025-21298 is a remote code execution (RCE) vulnerability stemming from a memory corruption issue in the ole32.dll library. 

Specifically, the flaw resides in the UtOlePresStmToContentsStm function, which processes OLE objects embedded in Rich Text Format (RTF) files. 

Attackers can exploit this vulnerability by sending a malicious email containing an RTF attachment. Simply opening or previewing the email in Microsoft Outlook triggers the vulnerability, enabling attackers to execute arbitrary code without requiring user interaction.

“When the victim opens or previews the email in Microsoft Outlook, the vulnerability is triggered, allowing the attacker to execute arbitrary code on the affected system,” OffSec researchers said.

Windows OLE Zero-Click Vulnerability Details

The vulnerability is classified as a “Use After Free” issue (CWE-416), where memory that has already been freed is improperly accessed. This occurs during the conversion of data from an “OlePres” stream to a “CONTENTS” stream within OLE storage. 

If an attacker crafts the RTF file to exploit this flaw, it can corrupt heap memory management structures, leading to arbitrary code execution.

A proof-of-concept (PoC) exploit has been published on GitHub, demonstrating how opening a malicious RTF file crashes Microsoft Word or Outlook. 

Security researchers have confirmed that exploitation can result in full system compromise, granting attackers the ability to:

• Install programs.
• Access or alter sensitive data.
• Create new accounts with full user privileges.

This zero-click vulnerability is particularly dangerous because it requires no user interaction beyond email previewing. 

It affects multiple Windows versions, including Windows 10, Windows 11, and various Windows Server editions. Organizations using Microsoft Outlook are especially at risk due to its widespread use for email communication.

Mitigation and Recommendations

Microsoft addressed this vulnerability in its January 2025 Patch Tuesday updates. Users and organizations are urged to apply these patches immediately.

For those unable to update promptly, Microsoft recommends configuring Outlook to read all emails in plain text format. 

This reduces the risk of automatic execution of malicious OLE objects but may impact email readability by removing rich content like images and animations.

Additional mitigation steps include:

• Avoid opening RTF files from untrusted sources.
• Implement least privilege principles to minimize potential damage from successful exploits.
• Use Sigma rules or other detection mechanisms to monitor suspicious interactions with .rtf files or OLE-related processes.

Security professionals can leverage tools like Microsoft Defender and third-party solutions to detect exploitation attempts. For instance:

Sigma rules can identify systems interacting with high-risk file types such as .rtf or .dll. Debugging tools like WinDbg can trace memory operations during file processing to confirm exploitation.

CVE-2025-21298 underscores the ongoing challenges of securing legacy technologies like OLE. Its zero-click nature and high impact make it a critical threat to organizations worldwide. 

Immediate patching and proactive monitoring are essential to mitigate risks associated with this vulnerability.

Investigate Real-World Malicious Links & Phishing Attacks With Threat Intelligence Lookup - Try for Free

The post Critical Windows OLE Zero-Click Vulnerability Let Attacker to Execute Arbitrary Code appeared first on Cyber Security News.