CVE-2023-6546 is a use-after-free vulnerability identified in the GSM 0710 tty multiplexor component of the Linux kernel as implemented in Red Hat Enterprise Linux 8. The issue stems from a race condition triggered when two threads simultaneously invoke the GSMIOC_SETCONF ioctl command on the same tty file descriptor while the gsm line discipline is active. This concurrency leads to improper handling of the gsm_dlci structure during the restart of the gsm mux, resulting in a use-after-free condition. Such memory corruption can be exploited by a local unprivileged user to escalate privileges, potentially gaining root-level access or other elevated capabilities. The vulnerability has a CVSS 3.1 base score of 7.0, indicating high severity, with attack vector local, attack complexity high, privileges required low, no user interaction, and impacts on confidentiality, integrity, and availability. Although no public exploits are known, the flaw poses a significant risk in environments where local user access is possible. The vulnerability affects Red Hat Enterprise Linux 8 systems that enable the gsm line discipline, which is typically used in telecom or embedded device contexts. The race condition and use-after-free vulnerability highlight the importance of proper synchronization in kernel ioctl handling to prevent memory corruption and privilege escalation.

For European organizations, this vulnerability poses a significant risk especially in sectors relying on Red Hat Enterprise Linux 8, such as telecommunications, critical infrastructure, and enterprises using embedded Linux systems with GSM multiplexing. Successful exploitation allows local attackers to escalate privileges, potentially leading to full system compromise, unauthorized access to sensitive data, disruption of services, and lateral movement within networks. Confidentiality, integrity, and availability of affected systems could be severely impacted. Organizations with multi-user environments or those providing local access to untrusted users are particularly vulnerable. The high attack complexity somewhat limits exploitation but does not eliminate risk, especially in environments where skilled attackers have local access. The absence of known exploits in the wild currently reduces immediate threat but patching remains critical to prevent future attacks.

1. Apply official patches and updates from Red Hat as soon as they become available to address CVE-2023-6546. 2. Restrict local user access to trusted personnel only, minimizing the risk of local exploitation. 3. Disable the gsm line discipline if it is not required for operational purposes to reduce the attack surface. 4. Implement strict access controls and monitoring on ioctl system calls, particularly GSMIOC_SETCONF, to detect anomalous or concurrent usage patterns. 5. Employ kernel security modules (e.g., SELinux) to enforce least privilege and limit the capabilities of local users. 6. Conduct regular audits of local user activities and system logs to identify potential exploitation attempts. 7. For embedded or telecom devices using GSM multiplexing, ensure firmware and kernel components are updated and hardened against race conditions. 8. Educate system administrators about the risks of race conditions and use-after-free vulnerabilities to improve incident response readiness.