CVE-2025-29974 is a medium-severity vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw is an integer underflow (CWE-191) occurring within the Windows Kernel, which can be exploited by an unauthorized attacker to disclose sensitive information over an adjacent network. An integer underflow happens when an arithmetic operation attempts to reduce a numeric value below its minimum representable value, causing it to wrap around to a very large number. In kernel-level code, such underflows can lead to incorrect memory calculations or buffer sizes, potentially exposing protected memory contents or causing information leakage. This vulnerability does not require privileges (PR:N) but does require user interaction (UI:R), and the attacker must be on an adjacent network (AV:A), such as the same local network segment or VPN. The impact is limited to confidentiality (C:H), with no effect on integrity or availability. There are no known exploits in the wild at the time of publication, and no patches have been linked yet. The vulnerability was reserved in March 2025 and published in May 2025. Given the kernel-level nature, exploitation could allow attackers to bypass some security boundaries to extract sensitive information from the affected system, which could be leveraged for further attacks or reconnaissance.

For European organizations, this vulnerability poses a risk primarily to confidentiality of sensitive data on Windows 10 Version 1809 systems. Many enterprises and public sector entities in Europe still operate legacy Windows 10 installations, especially in critical infrastructure, manufacturing, and government environments. An attacker on the same local network segment could exploit this flaw to gain unauthorized access to kernel memory information, potentially exposing credentials, cryptographic keys, or other sensitive information. This could facilitate lateral movement, privilege escalation, or targeted espionage. The requirement for user interaction and adjacency limits remote exploitation but does not eliminate risk in environments with shared networks or VPNs. Organizations with extensive Windows 10 1809 deployments, especially those in regulated sectors such as finance, healthcare, and energy, could face increased exposure. Additionally, the vulnerability could be leveraged in targeted attacks against European governmental or defense networks where Windows 10 1809 remains in use due to legacy application dependencies.

Given the absence of an official patch at the time of this report, European organizations should implement the following specific mitigations: 1) Identify and inventory all Windows 10 Version 1809 systems on the network to understand exposure. 2) Limit network adjacency exposure by segmenting networks, enforcing strict VLANs, and restricting lateral network traffic to minimize attacker proximity. 3) Enforce strong user interaction policies, such as disabling unnecessary user-initiated network connections or prompts that could trigger exploitation. 4) Employ host-based intrusion detection and prevention systems (HIDS/HIPS) to monitor for anomalous kernel-level activities or memory access patterns indicative of exploitation attempts. 5) Accelerate migration plans to newer, supported Windows versions with active security updates to eliminate exposure. 6) Monitor threat intelligence feeds for any emerging exploit code or proof-of-concept releases to respond rapidly. 7) Apply strict access controls and multi-factor authentication on network access points to reduce the risk of unauthorized user interaction. 8) Use network-level encryption and segmentation to reduce the risk of information disclosure over adjacent networks.