CVE-2026-20835 is a medium-severity vulnerability classified as CWE-125 (Out-of-bounds Read) affecting Microsoft Windows Server 2025, specifically the Server Core installation variant. The flaw exists in the Capability Access Management Service (camsvc), a component responsible for managing access capabilities within the operating system. An authorized attacker with local privileges can exploit this vulnerability to read memory outside the intended buffer boundaries. This out-of-bounds read can lead to the disclosure of sensitive information residing in adjacent memory areas, potentially exposing credentials, tokens, or other confidential data. The vulnerability does not require user interaction and does not allow for code execution or system modification, limiting its impact to confidentiality breaches. The CVSS v3.1 base score is 5.5, reflecting a medium severity level due to the local attack vector (AV:L), low attack complexity (AC:L), and the requirement for privileges (PR:L). The scope remains unchanged (S:U), and the impact is high on confidentiality (C:H) but none on integrity (I:N) or availability (A:N). No public exploit code or active exploitation has been reported to date. The vulnerability was reserved in December 2025 and published in January 2026, indicating recent discovery and disclosure. The absence of patch links suggests that fixes may be forthcoming or pending deployment. This vulnerability is particularly relevant to environments running Windows Server 2025 Server Core, which is commonly used in enterprise and data center settings due to its minimal footprint and reduced attack surface. Attackers with local access, such as malicious insiders or compromised accounts, could leverage this flaw to gain unauthorized access to sensitive information, potentially aiding further attacks or lateral movement within a network.

For European organizations, the primary impact of CVE-2026-20835 is the potential unauthorized disclosure of sensitive information stored in memory on Windows Server 2025 Server Core systems. This could include credentials, tokens, or other confidential data that attackers could use to escalate privileges or move laterally within networks. Sectors such as finance, healthcare, government, and critical infrastructure, which often rely on Windows Server environments, may be particularly at risk. Although the vulnerability does not allow code execution or system disruption, the confidentiality breach could undermine trust, lead to regulatory non-compliance (e.g., GDPR), and facilitate more severe attacks. The requirement for local privileges limits the threat to insiders or attackers who have already compromised a system to some extent, but it still represents a significant risk in environments with multiple administrators or shared access. The lack of known exploits reduces immediate risk but does not eliminate the potential for future weaponization. Organizations with automated monitoring and strict access controls may mitigate exposure, but those with lax local privilege management could face higher risks.

To mitigate CVE-2026-20835, European organizations should prioritize the following actions: 1) Monitor Microsoft security advisories closely and apply patches promptly once released, as no patch links are currently available. 2) Restrict local administrative privileges to the minimum number of trusted personnel to reduce the attack surface. 3) Implement strict access controls and auditing on servers running Windows Server 2025 Server Core to detect and prevent unauthorized local access. 4) Employ memory protection and integrity monitoring tools that can detect anomalous memory reads or suspicious behavior in camsvc or related processes. 5) Use endpoint detection and response (EDR) solutions to identify potential exploitation attempts or privilege escalations. 6) Conduct regular security training for administrators to recognize and report suspicious activities. 7) Consider network segmentation to isolate critical servers and limit lateral movement opportunities. 8) Review and harden server configurations to minimize unnecessary services and reduce the potential for privilege misuse. These targeted measures go beyond generic advice by focusing on controlling local access and monitoring the specific service involved.