CVE-2025-26677 is a high-severity vulnerability classified under CWE-400 (Uncontrolled Resource Consumption) affecting Microsoft Windows Server 2019, specifically version 10.0.17763.0. The vulnerability resides in the Remote Desktop Gateway Service, a critical component that enables secure remote access to internal network resources via Remote Desktop Protocol (RDP). An unauthorized attacker can exploit this flaw remotely without any authentication or user interaction, by sending specially crafted requests to the Remote Desktop Gateway Service. This triggers uncontrolled resource consumption, such as excessive CPU, memory, or network bandwidth usage, leading to a denial of service (DoS) condition. The CVSS 3.1 base score of 7.5 reflects the high impact on availability, with no impact on confidentiality or integrity. The attack vector is network-based with low attack complexity, and no privileges or user interaction are required, making exploitation feasible in unpatched environments. Although no known exploits are currently observed in the wild, the vulnerability's nature and ease of exploitation make it a significant risk for organizations relying on Windows Server 2019 Remote Desktop Gateway for remote access. The absence of published patches at the time of disclosure increases the urgency for mitigation and monitoring.

For European organizations, this vulnerability poses a substantial risk to business continuity and operational availability, especially for those heavily dependent on Remote Desktop Gateway Services for remote workforce access, cloud services, or hybrid infrastructure. A successful DoS attack could disrupt critical services, delay business processes, and cause financial losses. Sectors such as finance, healthcare, government, and critical infrastructure, which often use Windows Server 2019 for secure remote access, are particularly vulnerable. The disruption could also impact compliance with regulations like GDPR if service outages affect data availability or processing. Additionally, the vulnerability could be leveraged as part of multi-stage attacks, where denial of service is used as a diversion or to disable defenses. Given the network-based attack vector and lack of authentication requirements, attackers from outside the organization or within compromised networks can launch attacks with relative ease.

Organizations should prioritize the following specific mitigation steps: 1) Immediately audit and inventory all Windows Server 2019 instances running Remote Desktop Gateway Service, focusing on version 10.0.17763.0. 2) Apply any available security updates or patches from Microsoft as soon as they are released; monitor Microsoft security advisories closely. 3) In the absence of patches, implement network-level protections such as rate limiting and traffic filtering on Remote Desktop Gateway ports to limit the impact of resource exhaustion attempts. 4) Restrict Remote Desktop Gateway access to trusted IP ranges and enforce strict firewall rules to reduce exposure. 5) Enable and monitor detailed logging on Remote Desktop Gateway to detect abnormal traffic patterns indicative of resource consumption attacks. 6) Consider deploying Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with signatures or anomaly detection tuned for Remote Desktop Gateway traffic. 7) Educate IT staff on this vulnerability and prepare incident response plans specifically addressing potential DoS scenarios targeting Remote Desktop Gateway. 8) Evaluate alternative remote access solutions or temporary workarounds that reduce reliance on the vulnerable service until patches are applied.