CVE-2021-47547 is a medium-severity vulnerability identified in the Linux kernel's network driver code, specifically within the tulip driver for de4x5 network interface cards. The issue arises from an out-of-bounds array access in the 'lp->phy' array, which is defined with 8 elements indexed from 0 to 7. The vulnerability occurs when a loop iterates over this array and the loop counter 'k' reaches 8, causing an attempt to access 'lp->phy[8]', which is outside the valid bounds of the array. This out-of-bounds access can lead to undefined behavior, including potential memory corruption. The vulnerability requires local privileges (PR:L) and low attack complexity (AC:L), but no user interaction (UI:N) is needed. The impact is limited to integrity and availability, with no confidentiality impact. Exploitation could allow a local attacker with some privileges to cause a denial of service or potentially escalate privileges by corrupting kernel memory structures. The vulnerability has been patched in the Linux kernel, but no known exploits are currently reported in the wild. The affected versions are identified by specific commit hashes, indicating that the issue is present in certain kernel builds prior to the patch. The CVSS v3.1 base score is 4.4, reflecting a medium severity level.

For European organizations, this vulnerability poses a moderate risk primarily to systems running vulnerable Linux kernel versions with the tulip de4x5 network driver enabled. The impact includes potential denial of service or integrity compromise on affected hosts, which could disrupt critical network services or lead to local privilege escalation. Organizations relying on legacy or specialized hardware using the de4x5 driver may be particularly vulnerable. Given that the vulnerability requires local privileges, the threat is more significant in environments where untrusted users have shell or local access, such as multi-tenant servers, shared workstations, or development environments. The absence of known exploits reduces immediate risk, but the presence of a patch means that unpatched systems remain exposed. For European enterprises with strict uptime and security requirements, especially in sectors like finance, telecommunications, and critical infrastructure, this vulnerability could impact service reliability and system integrity if exploited.

1. Apply the official Linux kernel patches that address CVE-2021-47547 as soon as possible to eliminate the out-of-bounds access. 2. Identify and inventory systems running Linux kernels with the tulip de4x5 driver enabled, focusing on legacy or specialized hardware that may still use this driver. 3. Restrict local access to trusted users only and enforce strict access controls to minimize the risk of local exploitation. 4. Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR) and Kernel Page Table Isolation (KPTI) to reduce the impact of potential memory corruption. 5. Monitor system logs and kernel messages for anomalies that could indicate exploitation attempts or crashes related to the network driver. 6. Consider disabling the tulip de4x5 driver if it is not required, to eliminate the attack surface. 7. Incorporate this vulnerability into vulnerability management and patching workflows to ensure timely updates.