CVE-2026-20832 is a vulnerability identified in Microsoft Windows 10 Version 1809, specifically affecting the Remote Procedure Call (RPC) Interface Definition Language (IDL) component. The root cause is a double free condition (CWE-415), where the system attempts to free the same memory location twice, leading to memory corruption. This flaw can be exploited by an attacker with limited privileges (local access) to elevate their privileges to SYSTEM level, thereby gaining full control over the affected machine. The vulnerability does not require user interaction, which increases the risk of automated or stealthy exploitation once local access is obtained. The CVSS v3.1 base score is 7.8, indicating high severity, with the vector showing local attack vector (AV:L), low attack complexity (AC:L), requiring privileges (PR:L), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). Although no public exploits are known at this time, the nature of the vulnerability suggests that attackers could develop reliable exploits to escalate privileges on vulnerable systems. The affected version is Windows 10 1809 build 17763.0, a version still in use in some environments despite being superseded by newer releases. The vulnerability was reserved in December 2025 and published in January 2026, indicating recent discovery and disclosure. No official patches or mitigation links are currently provided, emphasizing the need for vigilance and interim protective measures.

For European organizations, the impact of CVE-2026-20832 can be severe. Successful exploitation allows attackers to elevate privileges from a limited user account to SYSTEM level, enabling full control over the affected system. This can lead to unauthorized access to sensitive data, disruption of critical services, and potential lateral movement within networks. Organizations in sectors such as government, finance, healthcare, and critical infrastructure are particularly at risk due to the sensitive nature of their data and operations. The vulnerability affects Windows 10 Version 1809, which may still be in use in legacy systems or environments where upgrading is delayed. The lack of user interaction requirement means that once local access is gained, exploitation can proceed without alerting users, increasing stealth and persistence risks. The high impact on confidentiality, integrity, and availability could result in data breaches, operational downtime, and significant financial and reputational damage. Additionally, the vulnerability could be leveraged by advanced persistent threat (APT) actors targeting European entities for espionage or sabotage. The absence of known exploits in the wild currently provides a window for proactive defense, but the risk of future exploitation remains high.

Given the absence of an official patch at this time, European organizations should implement specific mitigations to reduce risk. First, identify and inventory all systems running Windows 10 Version 1809 and prioritize them for upgrade to a supported and patched Windows version. Where immediate upgrade is not feasible, restrict local access to these systems by enforcing strict access controls and limiting user privileges to the minimum necessary. Employ application whitelisting and endpoint detection and response (EDR) solutions to monitor for suspicious behavior indicative of exploitation attempts, such as unusual memory operations or privilege escalation activities. Network segmentation should be used to isolate vulnerable systems from critical assets and reduce lateral movement opportunities. Regularly audit and harden RPC-related configurations to minimize exposure. Additionally, implement strict logging and monitoring of local privilege escalation attempts and review logs frequently. Educate IT staff about this specific vulnerability to ensure rapid response if exploitation is suspected. Finally, stay updated with Microsoft advisories for the release of official patches and apply them promptly once available.