A Critical Vulnerability Discovered in Windows Defender Firewall

On December 9, 2025, Microsoft officially announced a significant vulnerability — CVE-2025-62468 — identified in the Windows Defender Firewall Service. This flaw allows a user with elevated privileges to read certain portions of system memory (heap memory) without authorization.

The vulnerability falls under the Information Disclosure category, meaning it may lead to the exposure of sensitive data. Microsoft has rated it as Important and assigned a CVSS score of 4.4.

What is the root cause of the vulnerability?

The issue stems from an out-of-bounds read error. In this scenario, the Windows Defender Firewall Service component may read memory regions that do not belong to it.

Key points:

  • The attacker must have high-level privileges.
  • No user interaction is required.
  • System functionality is not affected, but confidentiality may be compromised.
  • It is not easily exploitable, but it poses a risk to internal systems where privileged users or malicious software are present.

Which Windows versions are affected?

Microsoft has released updates for several platforms:

  • Windows Server 2025
  • Windows Server 2022 (23H2 Core)
  • Windows 11 23H2, 24H2, 25H2 (x64 and ARM64)

Updates are available through Windows Update or Microsoft Update Catalog. Some versions also include security hotpatch options in addition to regular security patches.

What makes this vulnerability serious?

CVE-2025-62468 has the following characteristics:

  • Local attack vector (requires access to the system)
  • Low attack complexity
  • Administrator-level privileges required
  • No user interaction needed

This means the flaw is not directly exploitable by external attackers, but is dangerous for insiders or anyone who has already gained access to the system.

An attacker could extract sensitive memory data and use it for further attacks — such as capturing tokens, bypassing authentication, or moving laterally within the network.

Practical Recommendations for Administrators

1️⃣ Apply updates immediately

Microsoft’s official KB patches fully eliminate the vulnerability. Do not delay installing them.

2️⃣ Review administrator privileges

Remove unnecessary admin accounts and follow the principle of least privilege.

3️⃣ Monitor privileged logs

Pay attention to:

  • Suspicious administrator activity
  • Memory access anomalies
  • Irregular Firewall service behavior
    Enable additional detection rules in SIEM/EDR tools.

4️⃣ Check for potential credential or token exposure

If suspicious signs appear, initiate incident response procedures.

5️⃣ Protect internal infrastructure

Even though external exploitation is unlikely, malicious activity may occur inside the network. Conduct audits in isolated segments.

CVE-2025-62468 is a vulnerability in Windows Defender Firewall Service that allows unauthorized reading of certain memory regions. While it does not disrupt system functionality, it poses a risk to sensitive data confidentiality.

Microsoft has already released patches, so the primary mitigation is rapid deployment of updates.