CVE-2025-59509 is a vulnerability identified in Microsoft Windows 10 Version 1809 (build 10.0.17763.0) affecting the Windows Speech component. The issue is categorized under CWE-201, which involves the insertion of sensitive information into sent data. In this context, the vulnerability allows an authorized attacker with local access and low privileges to cause the Windows Speech service to insert sensitive information into data that is sent out, potentially disclosing confidential information. The attack does not require user interaction and does not affect the integrity or availability of the system, focusing solely on confidentiality. The CVSS v3.1 base score is 5.5, reflecting a medium severity rating. The attack vector is local (AV:L), with low attack complexity (AC:L), and privileges required are low (PR:L). The scope is unchanged (S:U), and the impact is high on confidentiality (C:H), with no impact on integrity (I:N) or availability (A:N). No known exploits have been reported in the wild, and no official patches have been linked at the time of publication. The vulnerability could be exploited by an attacker who has gained local access to the system, such as through compromised credentials or physical access, to extract sensitive speech-related data that the system sends out, potentially leading to information leakage. This is particularly concerning for environments where speech data contains sensitive or personal information.

For European organizations, the primary impact of CVE-2025-59509 is the potential unauthorized disclosure of sensitive information processed by Windows Speech services on affected Windows 10 Version 1809 systems. This could include confidential business communications, personally identifiable information (PII), or other sensitive data transmitted via speech recognition or related features. Sectors such as finance, healthcare, government, and critical infrastructure that rely on speech-enabled applications or services are at heightened risk. The confidentiality breach could lead to regulatory non-compliance under GDPR, reputational damage, and potential financial losses. Since the vulnerability requires local access with low privileges, the risk is elevated in environments where endpoint security is weak or where insider threats exist. The lack of impact on system integrity and availability means the threat is primarily data leakage rather than system disruption. The absence of known exploits reduces immediate risk but does not eliminate the need for proactive mitigation, especially in sensitive or high-value environments.

1. Restrict local access to systems running Windows 10 Version 1809, especially those with speech services enabled, by enforcing strict access controls and least privilege principles. 2. Monitor and audit local user activities and data transmissions related to Windows Speech services to detect unusual or unauthorized data flows. 3. Disable or limit Windows Speech features on endpoints where speech functionality is not required to reduce the attack surface. 4. Implement endpoint detection and response (EDR) solutions capable of identifying anomalous behavior associated with speech data handling. 5. Apply any forthcoming patches or updates from Microsoft promptly once available. 6. Educate users and administrators about the risks of local privilege misuse and enforce strong authentication mechanisms to prevent unauthorized local access. 7. Consider upgrading affected systems to a more recent, supported Windows version where this vulnerability is not present. 8. Use network segmentation to isolate sensitive systems and limit lateral movement opportunities for attackers with local access.