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. The flaw is due to incorrect calculation of buffer offsets when copying heap-stored data within the XIChangeDeviceProperty function in Xi/xiproperty.c and the RRChangeOutputProperty function in randr/rrproperty.c. These functions handle changes to device and output properties in the X server, a critical component managing graphical display and input devices. The incorrect offset calculation can lead to writing outside the allocated buffer boundaries, potentially corrupting memory. This memory corruption can be exploited by a local attacker with low privileges to escalate their privileges or cause a denial of service by crashing the X server. The vulnerability has a CVSS 3.1 score of 7.8, indicating high severity, with an attack vector limited to local access (AV:L), low attack complexity (AC:L), requiring privileges (PR:L), no user interaction (UI:N), and impacts on confidentiality, integrity, and availability all rated high (C:H/I:H/A:H). No known public exploits have been reported yet, but the vulnerability poses a significant risk in environments where attackers can gain local access, such as multi-user systems or systems exposed to untrusted users. The affected product is Red Hat Enterprise Linux 6 Extended Lifecycle Support, which is an older but still supported version for certain customers requiring extended maintenance. The lack of patch links suggests that fixes may be pending or available through Red Hat’s extended support channels.

For European organizations, this vulnerability poses a significant threat especially in sectors relying on legacy Red Hat Enterprise Linux 6 Extended Lifecycle Support systems, such as government, finance, manufacturing, and critical infrastructure. Exploitation could allow attackers with limited local access to escalate privileges, potentially gaining administrative control over affected systems. This could lead to unauthorized access to sensitive data, disruption of services, or further lateral movement within networks. The denial of service impact could disrupt critical operations relying on graphical interfaces or services dependent on the X server. Given the high confidentiality, integrity, and availability impacts, organizations with legacy RHEL 6 deployments must consider this vulnerability a priority. The threat is amplified in environments where multiple users have local access or where attackers can gain footholds through other means such as compromised credentials or insider threats.

1. Apply official patches from Red Hat as soon as they become available through Extended Lifecycle Support channels. 2. Restrict local access to systems running RHEL 6 Extended Lifecycle Support, limiting user accounts and enforcing strict access controls. 3. Monitor logs and system behavior for unusual activity related to X server property changes or crashes. 4. Consider isolating legacy systems from critical network segments to reduce risk of lateral movement. 5. Where patching is delayed, implement compensating controls such as disabling unnecessary X server features or restricting access to X server sockets. 6. Conduct regular security audits and vulnerability scans focusing on legacy systems. 7. Plan for migration to supported, updated operating system versions to reduce exposure to legacy vulnerabilities.