RCE Vulnerability in Windows Notepad Poses Risk of System Compromise

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RCE Vulnerability in Windows Notepad Poses Risk of System Compromise

Information:

Windows Notepad is a basic text editor that comes pre-installed with the Windows operating system. In its current version on Windows 11, it has been modernized as a Microsoft Store application, offering enhanced features such as multi-tab support, automatic file saving, and Markdown rendering. These improvements are designed to facilitate note-taking and the management of structured documents. Notepad remains a widely used tool across all types of users due to its simplicity and accessibility.

Incident:

CVE-2026-20841 is a high-severity Command Injection vulnerability (CVSS 7.8) affecting the Microsoft Store version of Windows Notepad from version 11.0.0 prior to 11.2510. The vulnerability was introduced following the addition of the Markdown rendering feature. It is classified under CWE-77 and may allow an attacker to achieve Remote Code Execution (RCE).

The root cause lies in insecure handling of protocol handlers within the Markdown renderer. When the application encounters a link inside a Markdown file, it attempts to process the link without properly validating or restricting potentially dangerous URI schemes (such as file:// or ms-appinstaller://) before passing them to the Windows Shell.

Attack Method:

The attacker creates a Markdown (.md) file that appears to be a normal text document but contains embedded malicious links.
The victim opens the file in Notepad and is tricked into clicking the link (user interactions I required).
Notepad processes the link and invokes the associated system protocol, potentially triggering actions such as executing powershell.exe to download malware or launching a malicious program via ms-appinstaller.

Impact: Because the malicious code is executed under the privileges of the currently logged-in user, the level of impact depends on that user’s permissions. If the user has Local Administrator privileges, an attacker could gain full control of the affected system.

Recommendation:

- Update Notepad to version 11.2510 or later.

- Avoid opening Markdown (.md) files received via email attachments or from untrusted links.

- If the Markdown feature is not required, consider disabling it in the Notepad Settings.

The important things is Security systems. We must concern and monitor as usual.
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References :

- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20841

- https://www.cve.org/CVERecord?id=CVE-2026-20841

- https://www.purple-ops.io/resources-hottest-cves/windows-notepad-rce-cve2026/

Weekly Interesting CVE

NO.	CVE Name	Published Date	Last Update	Device/Appplication/OS Target	Attack Type	CVSS Severity Rating	Detail	Solution	Reference
1	CVE-2025-36253	2/2/2026	3/2/2026	IBM Concert 1.0.0 through 2.1.0	Cryptographic Weakness	5.9	IBM Concert 1.0.0 through 2.1.0 uses weaker than expected cryptographic algorithms that could allow an attacker to decrypt highly sensitive information.	Upgrade to IBM Concert version 2.2.0 or later	https://nvd.nist.gov/vuln/detail/CVE-2025-36253
2	CVE-2026-1861	3/2/2026	4/2/2026	Google Chrome version before 144.0.7559.132	Heap Buffer Overflow	8.8	Heap buffer overflow in libvpx in Google Chrome prior to 144.0.7559.132 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.	Update Google Chrome to version 144.0.7559.132 or later	https://nvd.nist.gov/vuln/detail/CVE-2026-1861
3	CVE-2020-37074	3/2/2026	4/2/2026	Remote Desktop Audit version 2.3.0.157	Buffer Overflow	9.8	Remote Desktop Audit 2.3.0.157 contains a buffer overflow vulnerability that allows attackers to execute arbitrary code during the Add Computers Wizard file import process. Attackers can craft a malicious payload file to trigger a structured exception handler (SEH) bypass and execute shellcode when importing computer lists.	Update Remote Desktop Audit to a version newer than 2.3.0.157	https://nvd.nist.gov/vuln/detail/CVE-2020-37074
4	CVE-2024-35281	13/5/2025	5/2/2026	FortiClientMac version 7.4.2 and below, version 7.2.8 and below, all version 7.0 FortiVoiceUCDesktop all version 3.0	Improper Isolation or Compartmentalization	7.8	An improper isolation or compartmentalization vulnerability [CWE-653] in FortiClientMac version 7.4.2 and below, version 7.2.8 and below, 7.0 all versions and FortiVoiceUCDesktop 3.0 all versions desktop application may allow an authenticated attacker to inject code via Electron environment variables.	Update to FortiClientMac version ≥ 7.2.9 or 7.4.3 and above. Update FortiVoiceUCDesktop to the latest version.	https://nvd.nist.gov/vuln/detail/CVE-2024-35281
5	CVE-2026-25815	5/2/2026	5/2/2026	Fortinet FortiOS through 7.6.6	Cryptographic Weakness	3.2	Fortinet FortiOS through 7.6.6 allows attackers to decrypt LDAP credentials stored in device configuration files	Upgrade to FortiOS version higher than 7.6.6	https://nvd.nist.gov/vuln/detail/CVE-2026-25815

Malware News or Campaign IOC/IOA | EN

No	Campaign Name	Detection Date	Attack Type	Description	Mitigation/Remediation
1	Password guessing without AI: How attackers build targeted wordlists	09/02/2026	Brute Force, Credential Stuffing Wordlist Attack	Even though the cyber world in 2026 is filled with discussions about artificial intelligence (AI), many password attacks still rely on traditional and straightforward methods. One of the most effective techniques is building targeted wordlists using publicly available information such as social media profiles, company websites, or data leaked from breaches. Attackers can adapt these words and details into likely password combinations that match real user behavior, making password guessing highly effective without the need for AI.The main problem is that users often create passwords linked to personal information or repetitive patterns, such as adding numbers to the end of a name or using a birth year. Even with enforced complexity rules, these policies cannot fully protect against wordlist-based attacks, because human behavior remains predictable and exploitable.To counter this threat, experts recommend several key measures: blocking passwords derived from public or previously exposed data, enforcing minimum length and complexity requirements, enabling Multi-Factor Authentication (MFA), and aligning password policies with real-world attack scenarios rather than just theoretical standards.This case highlights that password security is not only about advanced technology but also about user behavior and organizational policy. Organizations that raise awareness among employees and implement strong protective measures gain a significant advantage in reducing risks from ongoing cyberattacks.	Block passwords that have been previously exposed or derived from public information Enforce the use of long and complex passwords Enable Multi-Factor Authentication (MFA) Align password policies with real-world attack scenarios rather than just theoretical requirements

Campaign Name

Detection Date

Attack

Type

Description

Mitigation/Remediation

Password guessing without AI: How attackers build targeted wordlists

09/02/2026

Brute Force, Credential Stuffing Wordlist Attack

Even though the cyber world in 2026 is filled with discussions about artificial intelligence (AI), many password attacks still rely on traditional and straightforward methods. One of the most effective techniques is building targeted wordlists using publicly available information such as social media profiles, company websites, or data leaked from breaches. Attackers can adapt these words and details into likely password combinations that match real user behavior, making password guessing highly effective without the need for AI.The main problem is that users often create passwords linked to personal information or repetitive patterns, such as adding numbers to the end of a name or using a birth year. Even with enforced complexity rules, these policies cannot fully protect against wordlist-based attacks, because human behavior remains predictable and exploitable.To counter this threat, experts recommend several key measures: blocking passwords derived from public or previously exposed data, enforcing minimum length and complexity requirements, enabling Multi-Factor Authentication (MFA), and aligning password policies with real-world attack scenarios rather than just theoretical standards.This case highlights that password security is not only about advanced technology but also about user behavior and organizational policy. Organizations that raise awareness among employees and implement strong protective measures gain a significant advantage in reducing risks from ongoing cyberattacks.

Block passwords that have been previously exposed or derived from public information
Enforce the use of long and complex passwords
Enable Multi-Factor Authentication (MFA)
Align password policies with real-world attack scenarios rather than just theoretical requirements

Ref: https://www.bleepingcomputer.com/news/security/password-guessing-without-ai-how-attackers-build-targeted-wordlists/

18 February 2026

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RCE Vulnerability in Windows Notepad Poses Risk of System Compromise

RCE Vulnerability in Windows Notepad Poses Risk of System Compromise

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