CVE-2025-24052 is a stack-based buffer overflow vulnerability categorized under CWE-121, affecting the Agere Modem driver (ltmdm64.sys) included in Windows 11 Version 25H2 (build 10.0.26200.0). The flaw arises from improper handling of input data within the driver, which can lead to overwriting the stack memory. This vulnerability allows an attacker with low-level privileges on the system to execute arbitrary code, potentially leading to full system compromise by escalating privileges and gaining control over system confidentiality, integrity, and availability. The vulnerability does not require user interaction but does require local access, making it exploitable by insiders or malware already running with limited privileges. Microsoft has addressed this issue by removing the vulnerable driver in the October cumulative update, which disables fax modem hardware relying on this driver. The removal indicates that the driver is deprecated and no longer supported, pushing users to transition away from legacy fax modem hardware. No public exploits have been reported yet, but the CVSS score of 7.8 reflects the high impact and moderate exploitability. The vulnerability is particularly relevant for environments where legacy fax modems are still in use, as these devices will cease to function post-update, potentially disrupting business operations if not planned for. The vulnerability was reserved early in 2025 and publicly disclosed in October 2025, with Microsoft recommending removal of dependencies on the affected hardware to mitigate risk.

For European organizations, the impact of CVE-2025-24052 is twofold: security risk and operational disruption. From a security perspective, exploitation could allow attackers to gain elevated privileges and execute arbitrary code, compromising sensitive data and critical systems. This is especially concerning for sectors with strict data protection regulations such as finance, healthcare, and government. Operationally, the removal of the ltmdm64.sys driver disables fax modem hardware dependent on it, which remains in use in some European industries for legacy communications, including legal, healthcare, and manufacturing sectors. Organizations that have not transitioned away from fax modems may face communication outages, impacting business continuity. The need to remove dependencies on this hardware may require investment in alternative communication technologies or infrastructure upgrades. Given the high CVSS score and the critical nature of the vulnerability, organizations must prioritize patching and hardware transition to avoid both security breaches and operational downtime.

1. Apply the October 2025 cumulative update for Windows 11 Version 25H2 immediately to remove the vulnerable ltmdm64.sys driver and eliminate the vulnerability. 2. Conduct an inventory of all fax modem hardware and software dependencies within the organization to identify systems relying on the affected driver. 3. Develop and implement a migration plan to replace legacy fax modem hardware with modern, supported communication solutions such as secure email, digital fax services, or VoIP-based fax alternatives. 4. Restrict local access to systems running Windows 11 25H2 to trusted personnel only, minimizing the risk of local exploitation. 5. Monitor systems for unusual local activity or attempts to exploit local vulnerabilities, using endpoint detection and response (EDR) tools. 6. Educate IT and security teams about the removal of the driver and the implications for legacy hardware to ensure smooth transition and avoid operational disruptions. 7. For environments where fax modems are critical and cannot be immediately replaced, consider isolating these systems in segmented network zones with strict access controls until migration is complete.