Multiple Microsoft Products Hit by “Use-After-Free” and Privilege Escalation Vulnerabilities: CVE-2025-59236 and Others

Estimated reading time: 10 minutes

Key takeaways:

  • Multiple Microsoft products are affected by “use-after-free” and privilege escalation vulnerabilities.
  • Successful exploitation could lead to code execution, security bypass, privilege escalation, or information disclosure.
  • Apply Microsoft’s security updates as soon as possible to protect your systems.
  • Implement proactive security measures like vulnerability scanning and EDR to mitigate the risk of exploitation.

Table of Contents:

Microsoft has recently addressed a series of vulnerabilities across its product line, including “use-after-free” flaws in Office applications and privilege escalation issues in Azure components. These vulnerabilities, detailed in Microsoft’s security updates, could allow attackers to execute code, bypass security features, or gain elevated privileges on affected systems. This blog post summarizes these vulnerabilities, their potential impact, and recommended remediations.

Understanding the Scope of CVE-2025-59236 and Other Microsoft Vulnerabilities

This month’s security updates address multiple vulnerabilities, each with its own potential impact and attack vector. Exploitation could lead to code execution, security bypass, privilege escalation, or information disclosure, depending on the specific vulnerability and the affected system. The vulnerabilities include:

  • CVE-2025-59236 (CVSS 8.4): A use-after-free vulnerability in Microsoft Office Excel.
  • CVE-2025-59227 (CVSS 7.8): A use-after-free vulnerability in Microsoft Office.
  • CVE-2025-59234 (CVSS 7.8): A use-after-free vulnerability in Microsoft Office.
  • CVE-2025-55247 (CVSS 7.3): An improper link resolution vulnerability in .NET.
  • CVE-2025-55248 (CVSS 4.8): Inadequate encryption strength in .NET, .NET Framework, and Visual Studio.
  • CVE-2025-58724 (CVSS 7.8): Improper access control in Azure Connected Machine Agent.
  • CVE-2025-55315 (CVSS 9.9): Inconsistent interpretation of HTTP requests in ASP.NET Core.
  • CVE-2025-47989 (CVSS 7.0): Improper access control in Azure Connected Machine Agent.
  • CVE-2025-55697 (CVSS 7.8): A heap-based buffer overflow in Azure Local.

Let’s break down what these vulnerabilities mean for your organization.

Use-After-Free Vulnerabilities in Microsoft Office (CVE-2025-59236, CVE-2025-59227, CVE-2025-59234)

Use-after-free vulnerabilities occur when a program attempts to use memory after it has been freed. This can lead to unpredictable behavior, including crashes or, more critically, the execution of arbitrary code by an attacker. In the context of Microsoft Office Excel, an attacker could craft a malicious Excel file that, when opened by a user, exploits this vulnerability to execute code on the user’s system. Successful exploitation requires user interaction, as the victim must open the malicious file.

This vulnerability arises from how .NET handles file access through links. An attacker could potentially create a malicious link that, when followed, allows them to elevate their privileges on the local system. This could enable them to perform actions they would normally be restricted from.

Inadequate Encryption Strength in .NET (CVE-2025-55248)

This vulnerability involves weak encryption algorithms used within .NET, .NET Framework, and Visual Studio. An attacker with network access could potentially intercept and decrypt sensitive information transmitted over the network. This is particularly concerning for applications that handle sensitive data, such as credentials or financial information.

Improper Access Control in Azure Connected Machine Agent (CVE-2025-58724, CVE-2025-47989)

The Azure Connected Machine Agent allows on-premises machines to be managed from Azure. These vulnerabilities could allow an attacker with local access to the machine to elevate their privileges. Successful exploitation could grant the attacker control over the agent and potentially the machine itself.

HTTP Request Smuggling in ASP.NET Core (CVE-2025-55315)

HTTP request smuggling vulnerabilities arise from inconsistencies in how different servers or proxies interpret HTTP requests. An attacker could exploit this to bypass security features or gain unauthorized access to resources. This is a particularly serious vulnerability, as it can be exploited remotely and could affect a wide range of applications built on ASP.NET Core.

Heap-Based Buffer Overflow in Azure Local (CVE-2025-55697)

A heap-based buffer overflow occurs when a program writes data beyond the allocated buffer in the heap memory region. An attacker could exploit this to overwrite adjacent memory regions, potentially leading to code execution with elevated privileges. This vulnerability, present in Azure Local, could allow an attacker with local access to escalate their privileges on the system.

Affected Products and Versions

These vulnerabilities affect a wide range of Microsoft products and versions, including:

  • Microsoft .NET Framework (various versions)
  • Microsoft Office Online Server
  • Microsoft Office LTSC for Mac 2021/2024
  • Microsoft Office for Android
  • Microsoft ASP.NET Core (various versions)
  • Microsoft 365 Apps for Enterprise
  • Microsoft Office 2019/LTSC 2021/LTSC 2024
  • Microsoft Visual Studio 2022 (various versions)
  • Microsoft Windows Server 2025
  • Microsoft Arc Enabled Servers – Azure Connected Machine Agent

A comprehensive list of affected versions is available in Microsoft’s security update guide.

Impact of Exploitation

The potential impact of these vulnerabilities is significant. Successful exploitation could lead to:

  • Code Execution: Attackers could execute arbitrary code on affected systems, potentially installing malware, stealing data, or taking control of the system.
  • Security Bypass: Attackers could bypass security features, gaining unauthorized access to sensitive resources or functionality.
  • Privilege Escalation: Attackers could elevate their privileges on the system, allowing them to perform actions they would normally be restricted from.
  • Information Disclosure: Attackers could gain access to sensitive information, such as credentials, financial data, or proprietary information.

Remediation Steps

Microsoft has released security updates to address these vulnerabilities. It is crucial to apply these updates as soon as possible to protect your systems.

  • Apply Microsoft Updates: Use Microsoft Automatic Update or the Microsoft Security Update Guide to search for and apply the appropriate patches for your systems.
  • Disable WSUS Server Role (If Applicable): As a temporary mitigation measure for the WSUS RCE vulnerability (CVE-2025-59287), disable the WSUS Server role on vulnerable systems if immediate patching is not possible.
  • Monitor for Suspicious Activity: Monitor your systems for any signs of suspicious activity, such as unusual network traffic, unexpected process executions, or unauthorized access attempts.

Actionable Advice

For Technical Readers:

  • Patch Management: Prioritize patching systems based on their criticality and exposure. Systems directly accessible from the internet or those handling sensitive data should be patched first.
  • Vulnerability Scanning: Regularly scan your systems for known vulnerabilities using a vulnerability scanner. This will help you identify systems that are missing critical patches.
  • Endpoint Detection and Response (EDR): Deploy an EDR solution to detect and respond to malicious activity on your endpoints. EDR solutions can provide visibility into endpoint activity and help you identify and contain threats.
  • Network Segmentation: Segment your network to limit the impact of a successful attack. This will prevent an attacker from moving laterally across your network.

For Business Leaders:

  • Cybersecurity Awareness Training: Conduct regular cybersecurity awareness training for your employees. This will help them identify and avoid phishing attacks and other social engineering tactics.
  • Incident Response Plan: Develop and maintain an incident response plan. This plan should outline the steps to take in the event of a security incident.
  • Security Budget: Allocate sufficient resources to cybersecurity. This includes investing in security tools, training, and personnel.
  • Supply Chain Risk Monitoring: Understand and mitigate the risks associated with your supply chain. Ensure that your vendors have adequate security measures in place.

Microsoft security dashboard showing CVE alerts

How PurpleOps Can Help

PurpleOps offers a range of services that can help organizations protect themselves against these and other cybersecurity threats. Our services include:

  • Cyber Threat Intelligence Platform: Provides real-time ransomware intelligence, dark web monitoring service, telegram threat monitoring, live ransomware API, underground forum intelligence and brand leak alerting. This can help you stay ahead of emerging threats and proactively defend your systems.
  • Breach Detection: PurpleOps offers advanced breach detection capabilities to identify and respond to security incidents quickly.
  • Supply Chain Risk Monitoring: We provide supply-chain risk monitoring services to help you assess and mitigate the risks associated with your vendors.
  • Penetration Testing: Our penetration testing services can help you identify vulnerabilities in your systems and applications.
  • Red Team Operations: We offer red team operations to simulate real-world attacks and assess your organization’s security posture.

Microsoft’s recent security updates address critical vulnerabilities that could have a significant impact on organizations. It is crucial to apply these updates as soon as possible and take other proactive steps to protect your systems and data. PurpleOps can help you assess your risk, implement appropriate security measures, and respond to security incidents.

To learn more about how PurpleOps can help protect your organization from cyber threats, explore our platform and services, or contact us for more information.

FAQ

Q: What is a use-after-free vulnerability?

A: A use-after-free vulnerability occurs when a program attempts to use memory after it has been freed. This can lead to unpredictable behavior, including crashes or the execution of arbitrary code.

Q: What is privilege escalation?

A: Privilege escalation is when an attacker gains elevated privileges on a system, allowing them to perform actions they would normally be restricted from.

Q: How do I apply Microsoft security updates?

A: You can use Microsoft Automatic Update or the Microsoft Security Update Guide to search for and apply the appropriate patches for your systems.

Q: What is EDR?

A: Endpoint Detection and Response (EDR) is a security solution that provides visibility into endpoint activity and helps you identify and contain threats.