CVE-2025-21343 in Windows
Summary
by MITRE • 01/14/2025
Windows Web Threat Defense User Service Information Disclosure Vulnerability
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Analysis
by VulDB Data Team • 06/22/2026
This vulnerability resides in the Windows Web Threat Defense user service component which is part of the broader Windows security architecture designed to protect against web-based threats and malicious content. The flaw manifests as an information disclosure issue that allows unauthorized access to sensitive data through improper access controls within the service. The vulnerability specifically affects the Windows Web Threat Defense service that operates at the user level and processes web threat intelligence data. According to industry standards, this type of vulnerability maps to CWE-200 Information Exposure and potentially CWE-501 Trust Boundary Violation when the service fails to properly validate access permissions. The technical implementation involves the service maintaining internal state information that should remain protected but is accessible through crafted requests or unauthorized access paths. This service operates with elevated privileges and maintains references to threat intelligence data, user browsing patterns, and potentially sensitive security information that should remain confidential.
The operational impact of this vulnerability extends beyond simple data exposure as it creates potential attack vectors for adversaries seeking to gather intelligence about system security posture and user behavior patterns. Attackers could exploit this information disclosure to understand the security controls in place, identify potential weaknesses in threat detection mechanisms, and gather data that could be used for more sophisticated attacks. The vulnerability may allow threat actors to extract browsing history, security event logs, or other sensitive metadata that would normally be protected within the Windows Web Threat Defense framework. This information could be particularly valuable for attackers planning targeted attacks or conducting reconnaissance activities against the system. The exposure of such data creates a significant risk to user privacy and system security, as it may reveal patterns of web usage that could be leveraged for social engineering attacks or to understand system vulnerabilities. From an ATT&CK perspective, this vulnerability could enable techniques such as T1082 System Information Discovery and T1552 Unsecured Credentials, allowing adversaries to gain deeper insights into the target environment.
Mitigation strategies for this vulnerability should focus on implementing proper access controls and privilege separation within the Windows Web Threat Defense service. System administrators should ensure that the service operates with minimal required privileges and that all access to sensitive data is properly authenticated and authorized. The recommended approach includes applying the latest security updates from Microsoft that address this specific information disclosure issue, as well as implementing network segmentation to limit access to the service. Organizations should also consider disabling the Web Threat Defense service if it is not required for their security posture, as this eliminates the attack surface entirely. Security monitoring should be enhanced to detect unauthorized access attempts to the service, and regular audits should be conducted to ensure proper access controls remain in place. Additionally, implementing proper input validation and access control mechanisms within the service itself would prevent unauthorized data exposure. The vulnerability demonstrates the importance of maintaining strict separation between different security service components and ensuring that each service operates with the principle of least privilege. Organizations should also consider implementing additional security controls such as application whitelisting and network access controls to further protect against exploitation of this type of information disclosure vulnerability.