CVE-2025-29974 is an integer underflow vulnerability identified in the Windows Kernel component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The vulnerability arises due to improper handling of integer values, specifically an underflow (wrap or wraparound) condition. This flaw can be triggered remotely by an unauthorized attacker over an adjacent network, meaning the attacker must be on the same local network segment or connected via a network that allows direct Layer 2 communication. Exploiting this vulnerability allows the attacker to disclose sensitive information from the affected system, compromising confidentiality. The vulnerability does not allow for integrity or availability impacts, nor does it require any privileges or authentication, but it does require some user interaction. The CVSS v3.1 base score is 5.7, categorizing it as a medium severity issue. The attack vector is adjacent network (AV:A), with low attack complexity (AC:L), no privileges required (PR:N), and user interaction required (UI:R). The scope remains unchanged (S:U), and the impact is high on confidentiality (C:H), but none on integrity (I:N) or availability (A:N). There are no known exploits in the wild at the time of publication, and no patches or mitigation links have been provided yet. The vulnerability is related to CWE-191 (Integer Underflow) and also tagged with CWE-125, which relates to out-of-bounds read, suggesting that the underflow may lead to memory disclosure. This vulnerability is significant because the Windows Kernel is a core component, and flaws here can have broad security implications. However, the requirement for user interaction and adjacency limits the attack surface somewhat.

For European organizations, this vulnerability poses a risk primarily to environments still running Windows 10 Version 1809, which is an older release and may still be present in legacy systems or specialized industrial environments. The ability for an attacker on the same local network to disclose sensitive information could lead to leakage of confidential data, including credentials, internal communications, or other protected information. This could facilitate further attacks such as lateral movement, privilege escalation, or targeted espionage. Sectors with high-value intellectual property or sensitive personal data, such as finance, healthcare, government, and critical infrastructure, could be particularly impacted. The medium severity rating reflects that while the vulnerability does not allow direct system compromise or denial of service, the confidentiality breach could undermine trust and compliance with data protection regulations like GDPR. Additionally, the requirement for user interaction and adjacency means that remote exploitation over the internet is unlikely, but insider threats or compromised devices within the network could exploit this vulnerability to escalate their access to sensitive data.

Given the lack of an official patch at the time of this report, European organizations should implement network segmentation to limit adjacency exposure, ensuring that sensitive systems running Windows 10 Version 1809 are isolated from less trusted network segments. Employ strict access controls and monitoring on local networks to detect unusual activity indicative of exploitation attempts. Disable or restrict unnecessary local network services and protocols that could be leveraged to trigger the vulnerability. Enforce strong user awareness training to minimize risky user interactions that could facilitate exploitation. Where possible, upgrade affected systems to a more recent, supported version of Windows 10 or Windows 11 that does not contain this vulnerability. Employ endpoint detection and response (EDR) solutions capable of identifying anomalous kernel-level activity. Additionally, conduct regular vulnerability assessments and penetration tests focusing on local network attack vectors. Finally, maintain up-to-date backups and incident response plans to quickly address any potential breaches stemming from this vulnerability.