Urgent patch from Microsoft: Why Outlook/Word users must update immediately
- Thảo Nguyên
- 22 hours ago
- 2 min read
Microsoft has officially released critical patches to address a series of severe security vulnerabilities in Outlook and Word. These flaws pose a risk of allowing attackers to execute remote malicious code simply through emails or carefully crafted Office documents. Alarmingly, users can become targets just by previewing the email content without even opening any attachments.
Dangerous vulnerabilities in the rendering mechanism
Three notable vulnerabilities in this release are CVE-2026-45456, CVE-2026-45458, and CVE-2026-47635. All are classified as critical, with CVSS scores around 8.4.
The core issue lies in how Outlook Classic uses the Word Rendering Engine to display message content. When a malicious email arrives, the moment a user selects it to view in the Preview Pane, the system automatically processes that content through Word. This process inadvertently triggers memory-related flaws, enabling attackers to run dangerous code on the victim's device completely without their knowledge.
How attackers exploit these flaws
These vulnerabilities exploit issues related to computer memory management (such as memory overwrite or data mishandling). When the application fails to properly control processes, attackers seize the opportunity to gain control.
The most dangerous aspect here is that the attack occurs "silently." Since Outlook automatically renders the email in the Preview Pane, threat actors do not need to trick users into downloading files or clicking any links. This makes these attacks much harder to defend against compared to traditional phishing tactics.
Threats to users and enterprises
Because Outlook and Word are indispensable tools in corporate, banking, and government environments, these vulnerabilities become prime targets for cybercriminals. If successfully exploited, attackers can cause severe consequences:
Executing remote malicious code on the user's computer.
Installing ransomware or backdoors.
Stealing account credentials and sensitive data.
Gaining control of enterprise systems and propagating malware across the entire internal network.
Although Microsoft has not yet recorded instances of these vulnerabilities being widely exploited in the wild, the company has categorized some of them as "Exploitation More Likely." This means there is a high probability that public exploits for these vulnerabilities will emerge in the near future.
What should users and businesses do right now?
The most critical solution right now is to immediately update the latest patches for the Office suite and Outlook.
In addition, businesses and organizations should proactively implement several supplementary security measures:
Disable or restrict the use of the Preview Pane: This helps mitigate risks before patches can be applied.
Enable protected view: This mode protects computers when opening documents downloaded from the internet.
Utilize control tools: Use Attack Surface Reduction (ASR) rules to block unusual processes originating from Office applications.
Email monitoring and filtering: Enhance attachment filtering and sandbox testing systems.
Raise awareness: Train employees to recognize phishing emails, even as attack vectors grow increasingly sophisticated.
Email remains a favorite gateway for cybercriminals. Regular software updates and maintaining a vigilant mindset are the best ways to protect personal data and enterprise systems.
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