CVE-2025-29842 is a vulnerability identified in the UrlMon component of Microsoft Windows 10 Version 1507 (build 10.0.10240.0). The flaw is categorized under CWE-349, which involves the acceptance of extraneous untrusted data alongside trusted data. This vulnerability allows an attacker to bypass security features remotely over a network by injecting or manipulating untrusted data that is improperly accepted as trusted by the UrlMon module. UrlMon is responsible for handling URL monikers and related security policies in Windows, often used in web content processing and COM interactions. The vulnerability has a CVSS 3.1 base score of 7.5, with vector AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H, indicating that exploitation is network-based, requires high attack complexity, no privileges, and user interaction, but results in high impact on confidentiality, integrity, and availability. The vulnerability was reserved in March 2025 and published in May 2025. No patches or known exploits are currently available, but the vulnerability poses a significant risk due to the potential for remote security feature bypass and system compromise. The affected product is an early Windows 10 version, which is largely out of mainstream support, but may still be in use in some environments.

The vulnerability allows attackers to bypass security features remotely, potentially leading to unauthorized access, data disclosure, data tampering, and system disruption. Given the high impact on confidentiality, integrity, and availability, exploitation could result in full system compromise or unauthorized execution of code within the context of the user. Organizations running Windows 10 Version 1507 are particularly vulnerable, especially if these systems are exposed to untrusted networks or users. The requirement for user interaction and high attack complexity somewhat limits exploitation likelihood, but targeted attacks against legacy systems remain a concern. The lack of patches increases risk exposure until remediation is available. This vulnerability could be leveraged in spear-phishing campaigns or drive-by downloads to bypass security controls, leading to broader network compromise and data breaches.

1. Immediately identify and isolate systems running Windows 10 Version 1507 to limit exposure. 2. Restrict network access to vulnerable hosts, especially from untrusted or external networks. 3. Employ network-level protections such as web filtering, intrusion detection/prevention systems (IDS/IPS), and endpoint detection and response (EDR) solutions to monitor for suspicious UrlMon activity or exploitation attempts. 4. Educate users to recognize and avoid interacting with suspicious links or content that could trigger exploitation. 5. Monitor vendor communications closely for patches or updates addressing this vulnerability and apply them promptly once available. 6. Consider upgrading legacy Windows 10 systems to supported versions with active security updates to eliminate exposure. 7. Implement application whitelisting and least privilege principles to reduce impact if exploitation occurs. 8. Conduct regular vulnerability assessments and penetration testing focusing on legacy systems to identify and remediate similar risks.