CVE-2021-47336 is a vulnerability identified in the Linux kernel's SMACK (Simplified Mandatory Access Control Kernel) filesystem interface, specifically within the smackfs module. The issue arises from improper validation of the byte count parameter in the smk_set_cipso() function, which is responsible for setting CIPSO (Common IP Security Option) labels used for security policy enforcement. The vulnerability stems from a patch (commit 7ef4c19d245f3dc2) intended to restrict the byte count in smackfs write functions but failing to apply the count > SMK_CIPSOMAX check correctly except for the SMK_FIXED24_FMT format case. This oversight means that for other formats, the byte count is not properly restricted, potentially allowing an attacker with write access to the smackfs interface to supply an excessive byte count. This could lead to memory corruption or other undefined behavior within the kernel, possibly resulting in privilege escalation or denial of service. The vulnerability affects Linux kernel versions prior to the patch date and is relevant to systems using SMACK for mandatory access control. There are no known exploits in the wild at this time, and no CVSS score has been assigned yet. The vulnerability was published on May 21, 2024, and has been acknowledged by the Linux project and CISA. The affected versions are identified by a specific commit hash, indicating the vulnerability is present in certain kernel builds before the fix was applied.

For European organizations, the impact of CVE-2021-47336 depends largely on their use of Linux systems with SMACK enabled, which is less common than other Linux security modules like SELinux or AppArmor but still used in some environments for mandatory access control. If exploited, this vulnerability could allow a local attacker with write permissions to the smackfs interface to cause memory corruption, potentially leading to privilege escalation to root or kernel-level code execution. This would compromise the confidentiality, integrity, and availability of affected systems. Critical infrastructure, government agencies, and enterprises relying on hardened Linux environments with SMACK could face significant risks, including unauthorized access to sensitive data, disruption of services, and lateral movement within networks. Given the Linux kernel's widespread use in servers, cloud infrastructure, and embedded devices across Europe, the vulnerability could have broad implications if exploited, especially in sectors with high security requirements such as finance, healthcare, and telecommunications.

European organizations should take the following specific mitigation steps: 1) Identify all Linux systems running kernels vulnerable to CVE-2021-47336, focusing on those with SMACK enabled. 2) Apply the official Linux kernel patches that restrict the byte count in smk_set_cipso() as per the commit 7ef4c19d245f3dc2 or later kernel releases that include this fix. 3) If immediate patching is not feasible, restrict access to the smackfs interface by limiting write permissions to trusted administrators only, using file system permissions and mandatory access controls. 4) Monitor system logs for unusual activity related to smackfs writes or kernel errors that could indicate exploitation attempts. 5) Incorporate this vulnerability into vulnerability management and incident response plans, ensuring rapid detection and remediation. 6) For embedded or specialized devices using SMACK, coordinate with vendors to obtain patched firmware or kernel updates. 7) Conduct security audits to verify that SMACK configurations do not expose unnecessary write access to unprivileged users.