CVE-2024-21307 is a high-severity use-after-free vulnerability (CWE-416) affecting Microsoft Windows 10 Version 1809, specifically build 10.0.17763.0. The flaw exists within the Remote Desktop Client component, which handles remote desktop protocol (RDP) sessions. A use-after-free vulnerability occurs when a program continues to use a pointer after the memory it points to has been freed, potentially leading to memory corruption. In this case, exploitation could allow a remote attacker to execute arbitrary code on the target system by sending specially crafted requests to the vulnerable Remote Desktop Client. The CVSS 3.1 base score is 7.5, reflecting a high severity with the following vector: AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H. This means the attack can be performed remotely over the network without privileges but requires user interaction (such as connecting to a malicious RDP server). The vulnerability impacts confidentiality, integrity, and availability, as successful exploitation could lead to full system compromise. No known exploits are currently reported in the wild, and no patches or mitigation links have been published yet. The vulnerability was publicly disclosed on January 9, 2024, with the reservation date on December 8, 2023. Given the affected product is Windows 10 Version 1809, which is an older but still in-use version, many organizations may remain exposed if they have not upgraded or applied mitigations. The vulnerability’s exploitation complexity is moderate due to the required user interaction and high attack complexity, but the impact is severe due to potential remote code execution with no privileges required on the victim system.

For European organizations, this vulnerability poses a significant risk, especially for those still running Windows 10 Version 1809 in their infrastructure. Remote Desktop is widely used for remote administration, teleworking, and support, making this an attractive attack vector. Successful exploitation could lead to unauthorized access, data breaches, ransomware deployment, or disruption of critical services. Sectors such as finance, healthcare, government, and critical infrastructure are particularly at risk due to the sensitivity of their data and operations. The requirement for user interaction (connecting to a malicious RDP server) means phishing or social engineering campaigns could be leveraged to trick users into initiating the connection. Given the high confidentiality, integrity, and availability impact, organizations could face regulatory penalties under GDPR if personal data is compromised. Additionally, the lack of patches at the time of disclosure increases the window of exposure. Organizations relying on legacy systems or with delayed patch management processes are especially vulnerable.

1. Immediate mitigation should focus on reducing exposure to untrusted RDP servers. Users should be educated and warned against connecting to unknown or suspicious remote desktop hosts. 2. Network-level protections such as firewall rules should restrict outbound RDP connections to only trusted servers. 3. Employ network segmentation to isolate systems running Windows 10 Version 1809 from untrusted networks. 4. Use multi-factor authentication (MFA) for remote desktop access to reduce risk if credentials are compromised. 5. Monitor network traffic for unusual RDP connection attempts or anomalies indicative of exploitation attempts. 6. Apply principle of least privilege to user accounts to limit potential damage from a compromised session. 7. Plan and expedite upgrade or patching of affected Windows 10 Version 1809 systems to a supported and patched version of Windows. 8. Deploy endpoint detection and response (EDR) solutions capable of detecting use-after-free exploitation techniques and suspicious process behaviors. 9. Stay alert for official patches or advisories from Microsoft and apply them promptly once available.