CVE-2026-21232 is a vulnerability classified under CWE-822 (Untrusted Pointer Dereference) found in the Windows HTTP.sys driver in Windows 11 version 22H3 (build 10.0.22631.0). HTTP.sys is a kernel-mode device driver that handles HTTP protocol requests and is critical for web services and network communication on Windows. The vulnerability arises when HTTP.sys improperly dereferences a pointer that can be controlled or influenced by an attacker with local authorized access. This flaw can lead to memory corruption, allowing an attacker to execute arbitrary code with elevated privileges, effectively escalating their rights on the system. The CVSS v3.1 score of 7.8 reflects high severity, with attack vector being local (AV:L), low attack complexity (AC:L), requiring privileges (PR:L), no user interaction (UI:N), and impacting confidentiality, integrity, and availability at a high level (C:H/I:H/A:H). The vulnerability does not require user interaction but does require the attacker to have some level of local access, such as a standard user account. No public exploits are known at this time, but the potential for privilege escalation makes it a critical concern for system security. The vulnerability was reserved in December 2025 and published in February 2026, indicating recent discovery and disclosure. No patches are currently linked, so mitigation relies on interim controls until updates are released.

For European organizations, the impact of CVE-2026-21232 is significant due to the widespread use of Windows 11 in enterprise environments. Successful exploitation allows an attacker with local access to escalate privileges to SYSTEM level, potentially gaining full control over affected machines. This can lead to unauthorized access to sensitive data, disruption of services, and the ability to deploy further malware or ransomware. Sectors such as finance, healthcare, government, and critical infrastructure are particularly at risk, as compromise of endpoints can cascade into broader network breaches. The vulnerability's local attack vector means insider threats or compromised user accounts pose a direct risk. Additionally, environments with shared workstations or weak local account management are more vulnerable. The lack of known exploits currently reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits once patches are released. The vulnerability could also be leveraged in targeted attacks against European organizations with high-value assets.

Until official patches are released by Microsoft, organizations should implement several specific mitigations: 1) Restrict local user privileges by enforcing the principle of least privilege and disabling unnecessary local accounts. 2) Use application whitelisting and endpoint detection and response (EDR) tools to monitor and block suspicious local activity indicative of privilege escalation attempts. 3) Harden systems by disabling or restricting HTTP.sys usage where feasible, especially on endpoints not requiring HTTP services. 4) Employ network segmentation to limit the impact of compromised local accounts. 5) Monitor Windows event logs for anomalies related to HTTP.sys and privilege escalation attempts. 6) Prepare for rapid deployment of patches once available by maintaining up-to-date asset inventories and patch management processes. 7) Educate users about the risks of local account compromise and enforce strong authentication mechanisms. These measures go beyond generic advice by focusing on local privilege management and proactive monitoring tailored to this vulnerability's characteristics.