CVE-2025-24056 is a heap-based buffer overflow vulnerability identified in the Windows Telephony Server component of Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw arises when the Telephony Server improperly handles input data, leading to a heap overflow condition that can be triggered remotely over a network without requiring prior authentication. Successful exploitation allows an attacker to execute arbitrary code with system-level privileges, potentially leading to full system compromise. The vulnerability requires user interaction, which might involve the victim responding to a crafted telephony request or similar network interaction. The CVSS v3.1 score of 8.8 reflects the high impact on confidentiality, integrity, and availability, combined with low attack complexity and no privileges required. Although no public exploits or patches are currently available, the vulnerability is publicly disclosed and tracked by CISA, indicating a known risk. The affected Windows 10 version 1809 is an older release, but still in use in some environments, particularly in legacy systems or organizations delaying upgrades. The vulnerability is classified under CWE-122, a common weakness related to unsafe memory handling leading to buffer overflows. This flaw could be leveraged by attackers to deploy malware, ransomware, or conduct espionage by gaining persistent control over affected systems.

For European organizations, the impact of CVE-2025-24056 is significant due to the potential for remote code execution without authentication, enabling attackers to compromise systems fully. Confidentiality is at risk as attackers could access sensitive data; integrity is threatened through unauthorized code execution and system manipulation; availability could be disrupted by system crashes or ransomware deployment. Organizations relying on Windows 10 Version 1809, especially those with exposed telephony services or legacy telephony infrastructure, face elevated risk. Critical sectors such as telecommunications, government, healthcare, and finance could experience operational disruptions or data breaches. The lack of a patch increases exposure time, and the requirement for user interaction may limit but not eliminate risk, as social engineering or automated triggers could facilitate exploitation. The threat is exacerbated in environments with weak network segmentation or inadequate firewall policies. European entities with legacy systems or slow patch cycles are particularly vulnerable, potentially leading to regulatory compliance issues under GDPR if personal data is compromised.

Given the absence of an official patch, European organizations should implement immediate compensating controls. First, restrict network access to the Telephony Server component by applying strict firewall rules to block inbound traffic on telephony-related ports from untrusted networks. Disable or uninstall the Telephony Server service if it is not required. Employ network segmentation to isolate legacy Windows 10 1809 systems from critical infrastructure and sensitive data stores. Monitor network traffic for anomalous telephony requests or unusual patterns indicative of exploitation attempts. Educate users about the risk of interacting with unexpected telephony prompts or calls that could trigger the vulnerability. Prioritize upgrading affected systems to a supported Windows version with security updates. Implement endpoint detection and response (EDR) solutions capable of detecting exploitation behaviors related to heap overflows and remote code execution. Maintain up-to-date backups and incident response plans tailored to potential ransomware or malware scenarios stemming from this vulnerability.