CVE-2021-46971 is a vulnerability identified in the Linux kernel's performance monitoring subsystem, specifically within the perf/core component. The issue arises from an unconditional call to the security_locked_down() function regardless of whether the PERF_SAMPLE_REGS_INTR bit is set in the attr.sample_type field. This unconditional call leads to unintended interactions with the SELinux lockdown hook implementation. SELinux's lockdown hook performs access control checks based on the current task's security context and policy permissions related to the "lockdown" class, which governs integrity and confidentiality constraints. When the lockdown hook is called unnecessarily, it generates superfluous permission checks and audit records, potentially causing confusion or misinterpretation of security logs. The root cause is that the lockdown state is queried even when its result is irrelevant, which is harmless for the Lockdown LSM but problematic for SELinux's lockdown hook. The fix involves modifying the code to check the sample_type first and only invoke the lockdown hook when the PERF_SAMPLE_REGS_INTR bit is set, ensuring that the access control decision is meaningful and audit records are accurate. This vulnerability does not appear to allow direct privilege escalation or code execution but can lead to misleading audit logs and potentially complicate security monitoring and incident response processes. No known exploits are reported in the wild, and the vulnerability was published on February 27, 2024. The affected versions correspond to a specific Linux kernel commit (b0c8fdc7fdb77586c3d1937050925b960743306e). No CVSS score has been assigned to this vulnerability yet.

For European organizations, the primary impact of CVE-2021-46971 lies in the potential degradation of security monitoring and audit accuracy when SELinux is deployed with lockdown policies. Misleading or excessive audit records can increase the workload on security teams, potentially masking real security events or causing alert fatigue. This can indirectly weaken the organization's ability to detect and respond to genuine threats promptly. Since SELinux is widely used in enterprise Linux distributions common in Europe (such as Red Hat Enterprise Linux, CentOS, and Fedora), organizations relying on SELinux lockdown policies may experience these audit anomalies. However, the vulnerability does not directly compromise system confidentiality, integrity, or availability, nor does it provide a direct attack vector for privilege escalation or denial of service. Therefore, the operational impact is moderate but relevant for security operations and compliance auditing. Organizations with stringent compliance requirements or those in regulated sectors (finance, healthcare, critical infrastructure) may find the audit inaccuracies particularly problematic, as they rely heavily on precise and trustworthy audit trails.

To mitigate CVE-2021-46971, European organizations should: 1) Apply the official Linux kernel patches that address this issue as soon as they become available from their Linux distribution vendors. 2) Review and update SELinux policies to ensure they are correctly configured and do not generate excessive or misleading audit logs due to this vulnerability. 3) Enhance security monitoring tools to filter or correlate audit records to reduce false positives caused by this issue until patches are applied. 4) Conduct thorough testing of performance monitoring and lockdown features in controlled environments before deploying updates in production, to verify that audit behavior is as expected. 5) Maintain up-to-date inventories of Linux kernel versions in use and prioritize patching of systems running affected kernel versions, especially those with SELinux lockdown enabled. 6) Educate security operations teams about the nature of this vulnerability to avoid misinterpretation of audit logs during incident investigations. These steps go beyond generic advice by focusing on the interaction between perf/core and SELinux lockdown hooks and the operational impact on audit integrity.