CVE-2026-21249 is a vulnerability in Microsoft Windows that allows external control of file names or paths in the Windows NTLM authentication mechanism. This vulnerability allows an unauthorized attacker to perform spoofing locally, potentially leading to unauthorized access or other malicious activities. With a CVSS score of 3.3, it is classified as low severity, but it still poses a risk that organizations should not overlook.
Organizations using affected Windows versions should prioritize investigating this vulnerability. Although the exploitability is low, the potential for local spoofing could lead to unauthorized actions within the system. Given its nature, the urgency for remediation is moderate. Organizations are advised to schedule remediation in their patch cycle.
The vulnerability was published on February 10, 2026, and affects multiple versions of Windows, including Windows 10 and Windows Server. The implications of this vulnerability highlight the importance of maintaining up-to-date software to prevent unauthorized exploitation.
Organizations should prioritize patching immediately to mitigate the risks associated with CVE-2026-21249. As the threat landscape continues to evolve, maintaining vigilance against even low-severity vulnerabilities is essential.
Vulnerability Details
The CVE description states that this vulnerability allows external control of file name or path in Windows NTLM, enabling unauthorized attackers to perform spoofing locally. The CWE classification for this vulnerability is CWE-73, which relates to improper neutralization of special elements in output used by a downstream component.
The CVSS score of 3.3 indicates a low severity classification, which suggests that while this vulnerability may not be critical, it requires attention. The attack vector is local, meaning that an attacker must have local access to the system to exploit this vulnerability. The attack complexity is low, with no privileges required and user interaction needed for exploitation.
The vulnerability affects several versions of Microsoft Windows, including Windows 10 (various builds) and Windows Server (2012, 2016, 2019, 2022, and 2025). Organizations should assess their systems to determine if they are using affected versions.
Technical Analysis
The root cause of CVE-2026-21249 lies in the improper handling of file names or paths within the Windows NTLM authentication mechanism. This vulnerability allows an attacker with local access to manipulate file paths, leading to potential spoofing attacks. The attack vector is classified as local, meaning that exploitation requires physical or remote desktop access to the affected system.
Given the low attack complexity, an attacker can exploit this vulnerability with minimal effort. No special privileges are required, but user interaction is necessary to carry out the attack. The impact on confidentiality is low, as the attacker may gain access to local resources but does not affect the integrity or availability of the system.
Risk & Impact Analysis
Risk to organizations includes potential unauthorized access to sensitive information or resources within the system. While the attack complexity is low, the requirement for user interaction limits the exploitability in many environments. However, if an attacker gains local access, the potential for spoofing could lead to further malicious activities.
As this vulnerability pertains to local spoofing, organizations should remain vigilant about physical security and user access controls. The urgency for addressing this vulnerability is moderate, as it should be scheduled for remediation in the next patch cycle.
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The following versions of Microsoft Windows are affected by this vulnerability: Windows 10 (versions 1607, 1809, 21H2, 22H2), Windows 11 (versions 23H2, 24H2, 25H2), and various Windows Server editions (2012, 2016, 2019, 2022, and 2025). Organizations should ensure that they update affected systems to mitigate this vulnerability.
Mitigation & Remediation
Organizations should apply the necessary patches to the affected Windows versions as soon as possible. Regular software updates and security patches are critical in maintaining system integrity. If immediate patching is not feasible, organizations should implement configuration hardening and network controls to limit access to the affected systems until the patches can be applied.
For further guidance, organizations can consult our penetration testing services to identify potential weaknesses in their systems.
Detection Guidance
To detect potential exploitation of CVE-2026-21249, organizations should monitor logs for unusual file access patterns or attempts to manipulate file paths within the NTLM authentication process. Behavioral anomalies indicating unauthorized access attempts should be investigated promptly.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2026-21249 highlights the need for organizations to maintain robust security practices around file access controls. As vulnerabilities like these can be exploited by attackers with local access, it emphasizes the importance of protecting physical and remote access to systems.
Patterns of local exploitation underscore the necessity for security teams to stay vigilant against even low-severity vulnerabilities. Regular assessments, including penetration testing methodology, can help identify potential weaknesses before they are exploited.
In conclusion, organizations should prioritize ongoing training and awareness programs for employees to mitigate risks associated with local vulnerabilities. This proactive approach is essential for maintaining a secure environment.
For more information on how to enhance security, organizations can explore our resources on vulnerability management programs and consider implementing regular security assessments.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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