CVE-2021-47055 is a vulnerability identified in the Linux kernel's memory technology device (MTD) subsystem, specifically related to the handling of certain ioctl operations that modify protection bits and bad block tables on flash memory devices. The vulnerability concerns the lack of proper write permission checks for ioctl commands such as MEMLOCK, MEMUNLOCK, OTPLOCK, and MEMSETBADBLOCK. These ioctls are used to modify protection bits on flash memory devices, including SPI-NOR flashes, where MEMLOCK and OTPLOCK can be write-once operations due to hardware constraints (e.g., WP# pin tied to ground). MEMSETBADBLOCK modifies the bad block table, which is critical for flash memory reliability and data integrity. The core issue is that these operations require write permissions to prevent unauthorized modification, but prior to the fix, the kernel did not enforce these permissions correctly, potentially allowing unauthorized users or processes to alter protection bits or bad block tables. This could lead to unauthorized locking or unlocking of memory regions, or corrupting the bad block table, which may cause data corruption, denial of service, or bypass of hardware protection mechanisms. The vulnerability affects multiple Linux kernel versions identified by specific commit hashes. There are no known exploits in the wild, and no CVSS score has been assigned yet. The fix involves enforcing write permission checks on these ioctl operations to ensure only authorized users can perform these sensitive modifications.

For European organizations, this vulnerability poses a risk primarily to systems running vulnerable Linux kernel versions that utilize MTD devices, such as embedded systems, IoT devices, network appliances, and industrial control systems. Unauthorized modification of protection bits or bad block tables could lead to data corruption or device malfunction, potentially causing service disruptions or loss of critical data. In sectors like manufacturing, telecommunications, and critical infrastructure, where embedded Linux devices are common, exploitation could impact operational continuity. Although no exploits are currently known, the potential for privilege escalation or denial of service exists if an attacker gains local access. This could be particularly impactful in environments with multi-tenant systems or where untrusted users have some level of system access. The vulnerability does not appear to allow remote exploitation without prior access, limiting its impact to scenarios where attackers have local or privileged access. However, given the widespread use of Linux in European IT and OT environments, the vulnerability warrants prompt attention to avoid potential exploitation and maintain system integrity.

European organizations should prioritize updating their Linux kernels to versions that include the patch for CVE-2021-47055. Specifically, kernel maintainers and system administrators should verify that the MTD subsystem enforces write permissions on MEMLOCK, MEMUNLOCK, OTPLOCK, and MEMSETBADBLOCK ioctl operations. For embedded and IoT devices, firmware updates incorporating the patched kernel should be deployed. Additionally, organizations should audit user permissions to ensure that only trusted administrators have write access to devices exposing MTD interfaces. Implementing strict access controls and monitoring for unusual ioctl usage can help detect attempts to exploit this vulnerability. For systems where immediate patching is not feasible, consider disabling or restricting access to MTD ioctl interfaces where possible. Regularly review and apply security advisories from Linux kernel maintainers and vendors providing embedded Linux distributions. Finally, conduct thorough testing of updated kernels in controlled environments before wide deployment to avoid unintended disruptions.