CVE-2021-47580 is a vulnerability identified in the Linux kernel's SCSI debug driver (scsi_debug). The root cause lies in the misuse of the min_t() macro, which was originally using the "int" type instead of "u32" (unsigned 32-bit integer). This type mismatch leads to sign extension issues where larger values are incorrectly interpreted, causing a stack out-of-bounds (OOB) condition. Specifically, the vulnerability manifests as a stack buffer overflow during memory copy operations within the SCSI debug driver, as evidenced by kernel address sanitizer (KASAN) reports indicating stack-out-of-bounds reads in memcpy calls. The stack OOB can corrupt kernel memory, potentially leading to system instability, crashes (denial of service), or escalation of privileges if exploited. The vulnerability requires local privileges (low complexity) and no user interaction, but it does require some level of access (PR:L) to the system. The CVSS v3.1 score is 6.6 (medium severity), reflecting a high impact on confidentiality, limited impact on integrity, and limited impact on availability. The vulnerability affects Linux kernel versions containing the faulty scsi_debug driver code prior to the patch that changes min_t() to use the correct unsigned type. The scsi_debug driver is primarily used for testing and debugging SCSI subsystems, but it is present in many Linux distributions and environments, including virtualized and containerized setups. Exploitation could allow an attacker with local access to cause kernel memory corruption, potentially leading to privilege escalation or denial of service. No known exploits are currently reported in the wild. The vulnerability was published on June 19, 2024, and has been addressed by correcting the type used in min_t() to prevent stack OOB conditions.

For European organizations, the impact of CVE-2021-47580 depends on the deployment of Linux systems running vulnerable kernel versions with the scsi_debug driver enabled. Many enterprises, research institutions, and cloud providers in Europe use Linux extensively, including kernels with scsi_debug for testing or development environments. If exploited, this vulnerability could allow a local attacker to corrupt kernel memory, potentially leading to privilege escalation or denial of service. This could compromise confidentiality by exposing sensitive kernel memory contents, impact system integrity by corrupting kernel data structures, and affect availability through crashes. Organizations running virtualized environments or development/test servers with scsi_debug enabled are particularly at risk. While the vulnerability requires local access, insider threats or attackers who gain initial footholds could leverage this flaw to escalate privileges and move laterally within networks. This elevates the risk profile for critical infrastructure, financial institutions, and government agencies in Europe that rely on Linux-based systems. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time. The medium severity rating suggests that while not the highest priority, timely patching is important to maintain system security and stability.

1. Apply Kernel Updates: Immediately update Linux kernels to versions where the scsi_debug driver has been patched to fix the min_t() type usage. Use vendor-provided or distribution-specific kernel updates to ensure official patches are applied. 2. Disable scsi_debug Driver: If scsi_debug is not required in production or critical environments, disable or blacklist the module to eliminate the attack surface. 3. Restrict Local Access: Enforce strict access controls and user privilege management to limit who can execute code or commands on affected Linux hosts, reducing the risk of local exploitation. 4. Monitor Kernel Logs: Implement monitoring for kernel warnings or KASAN reports that could indicate attempts to exploit stack OOB conditions or memory corruption. 5. Harden Development/Test Environments: Since scsi_debug is often used in testing, ensure these environments are isolated from production networks and have limited user access. 6. Use Security Modules: Employ Linux Security Modules (e.g., SELinux, AppArmor) to restrict the capabilities of processes that might interact with SCSI devices or the scsi_debug driver. 7. Incident Response Preparedness: Prepare for potential exploitation by having incident detection and response plans focused on kernel-level anomalies and privilege escalation attempts. These mitigations go beyond generic advice by focusing on the specific driver and usage context of the vulnerability.