Today is the second Tuesday of the month which means it’s time for another round of “Patch Tuesday updates“. Microsoft recently released its monthly security updates for January 2025, addressing 159 vulnerabilities across its product ecosystem. The latest patch update is about both security and non-security improvements, especially if you did not install the last few optional updates. This article provides an overview of the key updates and emphasizes the importance of timely patching.
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Why Patch Tuesday Matters
Patch Tuesday is Microsoft’s monthly release of security updates designed to fix vulnerabilities in its software, including Windows operating systems, Office applications, server products like Exchange and SQL Server, and other components. These vulnerabilities can be exploited by malicious actors to gain unauthorized access to systems, steal data, disrupt operations, or spread malware. Applying these updates promptly is essential to mitigate these risks.
Patch Tuesday updates are cumulative updates that usually only include minor patches and security fixes.
Patch Tuesday update January 2025
Microsoft’s January 2025 Patch Tuesday comes with fixes for 159 flaws, among these are 10 Critical vulnerabilities and eight zero-days affecting the Windows Hyper-V NT Kernel Integration VSP, Microsoft Access, Windows App Package Installer and Windows Themes.
The number of bugs in each vulnerability category is listed below:
- 40 Elevation of Privilege Vulnerabilities
- 14 Security Feature Bypass Vulnerabilities
- 58 Remote Code Execution Vulnerabilities
- 24 Information Disclosure Vulnerabilities
- 20 Denial of Service Vulnerabilities
- 5 Spoofing Vulnerabilities
For information about the non-security Windows updates, you can read about today’s Windows 10 KB5049981 updates and the Windows 11 KB5050009 update.
Eight zero-day vulnerability
- CVE-2025-21333, CVE-2025-21334, & CVE-2025-21335: Hyper-V Elevation of Privilege: These three are closely related and affect Hyper-V, Microsoft’s virtualization technology. Imagine Hyper-V as a way to run multiple computers within your computer. These vulnerabilities could allow someone with access to one of those virtual computers to break out and gain control of the main computer (the host). This is a serious issue because it grants them “SYSTEM” privileges, meaning they have complete control. Because these were actively being used by attackers, CISA (Cybersecurity and Infrastructure Security Agency) urged everyone to patch quickly.
- CVE-2025-21366, CVE-2025-21395, & CVE-2025-21186: Microsoft Access Remote Code Execution: These three also go together and target Microsoft Access, a database program. These flaws could allow an attacker to remotely run code on a victim’s computer just by getting them to interact with a specially crafted Access file. Microsoft’s fix was to block certain file types (like .accdb, .accde, etc.) that are commonly used with Access, preventing these malicious files from being opened.
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CVE-2025-21275: Windows App Package Installer Elevation of Privilege: This vulnerability affects the way Windows installs apps. It could allow an attacker to gain “SYSTEM” privileges—full control of the computer—during the app installation process. This means a seemingly harmless app could actually be a way for an attacker to take over.
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CVE-2025-21308: Windows Themes Spoofing: This one targets Windows themes, which are ways to customize the look of your computer. This vulnerability could allow an attacker to trick a user into loading a malicious file disguised as a theme. While it requires the user to do something (load the file), it’s still dangerous because it relies on deception.
Ten Critical Severity Vulnerabilities Patched
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CVE-2025-21294: Microsoft Digest Authentication Remote Code Execution: Digest Authentication is a way for computers to verify your identity without sending your password directly. This vulnerability involves a “race condition,” meaning the attacker has to perform actions at precisely the right moment to exploit the flaw. If successful, they could run code on the affected system.
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CVE-2025-21295: SPNEGO Extended Negotiation (NEGOEX) Remote Code Execution: SPNEGO is a mechanism that helps computers agree on how to authenticate each other. This vulnerability requires the attacker to manipulate system operations in a specific way. If they succeed, they can remotely run code on the target computer without needing any user interaction.
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CVE-2025-21296: BranchCache Remote Code Execution: BranchCache helps speed up network access in branch offices by caching frequently accessed files. This vulnerability also involves a “race condition,” meaning timing is crucial for exploitation. Successful exploitation could lead to remote code execution.
- CVE-2025-21297 & CVE-2025-21309: Windows Remote Desktop Services Remote Code Execution: Remote Desktop Services (RDS) allows you to control a computer remotely. These vulnerabilities, again involving “race conditions,” could allow an attacker to run code on a system that uses the Remote Desktop Gateway.
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CVE-2025-21298: Windows OLE Remote Code Execution: OLE (Object Linking and Embedding) allows you to embed content from one application into another (like a chart from Excel in a Word document). This vulnerability could be exploited via a specially crafted email. If the victim opens the email with a vulnerable version of Outlook, the attacker could run code on their machine.
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CVE-2025-21307: Windows Reliable Multicast Transport Driver (RMCAST) Remote Code Execution: RMCAST is a component that helps send data to multiple recipients at once. This vulnerability is particularly concerning because an attacker could exploit it by simply sending specially crafted network packets to a vulnerable server, without needing any user interaction.
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CVE-2025-21311: Windows NTLM V1 Elevation of Privilege: NTLM V1 is an older authentication protocol. This vulnerability could allow an attacker to gain higher-level privileges on a system, potentially giving them administrative control.
- CVE-2025-21354 & CVE-2025-21362: Microsoft Excel Remote Code Execution: These vulnerabilities in Excel could allow an attacker to run code on a victim’s computer if they open a specially crafted Excel file.
Key takeaways about these critical vulnerabilities:
- Remote Code Execution (RCE): Many of these vulnerabilities allow for RCE, meaning an attacker can remotely execute code on a vulnerable system. This is a serious threat as it gives them significant control.
- Race Conditions: Several vulnerabilities rely on “race conditions,” which require precise timing to exploit. However, this doesn’t make them less dangerous.
- No User Interaction: Some of these vulnerabilities, like the RMCAST one, can be exploited without any action from the user, making them especially dangerous.
How to Obtain and Install the Updates
The primary method for obtaining and installing these updates is through Windows Update:
- Windows Update: Go to Settings > Update & Security > Windows Update (or equivalent in older Windows versions) and check for updates.
- WSUS/SCCM: Organizations using Windows Server Update Services (WSUS) or System Center Configuration Manager (SCCM) can deploy updates through their centralized management systems.
- Microsoft Update Catalog: For specific updates or offline installations, you can download them directly from the Microsoft Update Catalog website.
Important note:
- Focus on installing critical updates first, as they address the most severe vulnerabilities.
- Enable automatic updates to ensure that security patches are installed promptly.
- Before deploying updates to production systems, it’s recommended to test them in a non-production environment to identify any potential compatibility issues.
- Regularly check the Microsoft Security Update Guide for detailed information about released updates.
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