CVE-2023-5367 is an out-of-bounds write vulnerability identified in the xorg-x11-server component of Red Hat Enterprise Linux 6 Extended Lifecycle Support (ELS). The vulnerability stems from improper calculation of buffer offsets when copying heap-stored data within two key functions: XIChangeDeviceProperty in Xi/xiproperty.c and RRChangeOutputProperty in randr/rrproperty.c. These functions are responsible for handling changes to device properties and output properties in the X Window System server, which manages graphical display and input devices. The incorrect offset calculation can cause memory corruption through out-of-bounds writes, potentially allowing an attacker with local privileges to escalate their privileges or cause a denial of service by crashing the X server. The CVSS v3.1 score is 7.8 (high), reflecting high impact on confidentiality, integrity, and availability, with attack vector local, low attack complexity, and requiring low privileges but no user interaction. The vulnerability affects systems running RHEL 6 ELS with the vulnerable xorg-x11-server version. No public exploits or active exploitation have been reported yet, but the flaw's nature makes it a significant risk, especially in environments where RHEL 6 is still maintained for legacy applications. The flaw could be leveraged to gain elevated privileges or disrupt critical graphical services, impacting system stability and security.

For European organizations, the impact of CVE-2023-5367 can be substantial, particularly in sectors relying on legacy RHEL 6 ELS deployments such as manufacturing, government, and critical infrastructure. Successful exploitation could allow attackers to escalate privileges locally, potentially gaining administrative control over affected systems. This could lead to unauthorized access to sensitive data, manipulation of system configurations, or disruption of services through denial of service attacks targeting the X server. Given that the X server is integral to graphical user interfaces, its compromise could affect user productivity and system availability. The vulnerability's local attack vector means that insider threats or attackers with initial footholds could leverage this flaw to deepen their access. European organizations with strict compliance requirements may face regulatory and reputational risks if this vulnerability is exploited. The absence of known exploits in the wild provides a window for proactive mitigation, but the high severity score underscores the urgency of addressing the issue.

To mitigate CVE-2023-5367 effectively, European organizations should: 1) Monitor Red Hat advisories closely and apply official patches or updates for xorg-x11-server on RHEL 6 ELS as soon as they become available, as no patch links are currently provided. 2) Restrict local system access by enforcing strict user permissions and limiting login capabilities to trusted personnel only, reducing the risk of local exploitation. 3) Employ application whitelisting and endpoint detection solutions to identify anomalous behavior indicative of exploitation attempts targeting the X server. 4) Consider isolating legacy RHEL 6 systems from critical networks or migrating critical workloads to supported operating system versions to reduce exposure. 5) Conduct regular security audits and vulnerability scans focusing on legacy systems to detect unpatched instances. 6) Implement robust logging and monitoring of X server activities to detect unusual property change requests that may signal exploitation attempts. 7) Educate system administrators about the risks of legacy software and the importance of timely patching and access controls. These steps go beyond generic advice by focusing on legacy system management, local access restrictions, and proactive detection tailored to this vulnerability's characteristics.