CVE-2023-5574 is a use-after-free vulnerability identified in the Xvfb (X virtual framebuffer) server component of Red Hat Enterprise Linux 9. The issue arises specifically when Xvfb is configured in a legacy multi-screen setup known as Zaphod mode, which involves multiple protocol screens. The vulnerability is triggered when a pointer is warped from screen 1 to screen 0 during the shutdown or reset process of the Xvfb server. This pointer warping leads to a use-after-free condition, where memory that has been freed is accessed again, causing memory corruption. Such corruption can be exploited to escalate privileges or cause a denial of service by crashing the Xvfb server. The CVSS 3.1 base score is 7.0, reflecting high severity, with attack vector local (AV:L), attack complexity high (AC:H), privileges required low (PR:L), no user interaction (UI:N), unchanged scope (S:U), and high impacts on confidentiality, integrity, and availability (C:H/I:H/A:H). Exploitation requires local access and a very specific legacy configuration, limiting the attack surface. No known exploits are currently reported in the wild. The vulnerability affects Red Hat Enterprise Linux 9 systems running Xvfb with Zaphod mode enabled, which is uncommon in modern deployments but may still be present in legacy or specialized environments. The flaw underscores the risks of legacy configurations and the importance of secure shutdown procedures in graphical server components.

For European organizations, the impact of CVE-2023-5574 can be significant in environments where Red Hat Enterprise Linux 9 is deployed with Xvfb configured in Zaphod mode. The vulnerability allows a local attacker with low privileges to potentially escalate their privileges to higher levels or cause denial of service by crashing the Xvfb server, impacting system availability and potentially confidentiality and integrity of graphical session data. This could disrupt critical services relying on graphical interfaces or virtual framebuffers, such as automated testing environments, remote graphical sessions, or legacy applications. Organizations in sectors like finance, government, research, and critical infrastructure that use Red Hat Enterprise Linux extensively may face operational disruptions or security breaches if the vulnerability is exploited. Although exploitation complexity is high and requires specific configurations, the potential for privilege escalation elevates the risk profile. The absence of known exploits reduces immediate threat but does not eliminate risk, especially in targeted attacks or insider threat scenarios.

To mitigate CVE-2023-5574, European organizations should first identify any systems running Red Hat Enterprise Linux 9 with Xvfb configured in Zaphod mode. Since this configuration is legacy and uncommon, disabling Zaphod mode or avoiding multi-screen setups with multiple protocol screens is recommended. Organizations should monitor Red Hat advisories closely and apply official patches or updates as soon as they become available. In the interim, restrict local access to trusted users only, as exploitation requires local privileges. Implement strict access controls and auditing on systems running Xvfb to detect any suspicious activity. Consider isolating vulnerable systems or migrating workloads to environments not using Xvfb or legacy multi-screen configurations. Additionally, review shutdown and reset procedures for graphical servers to ensure they do not trigger unsafe pointer operations. Regularly update and harden Linux systems to reduce attack surfaces and maintain secure configurations. Employ endpoint detection and response tools to monitor for anomalous behavior indicative of exploitation attempts.