CVE-2021-47159 is a vulnerability identified in the Linux kernel's Distributed Switch Architecture (DSA) networking subsystem. The flaw arises in the handling of the get_sset_count() function pointer within the DSA driver operations. Specifically, if the get_sset_count() call fails, it returns a negative error code (e.g., -EOPNOTSUPP). However, the code incorrectly assigns this negative error code to an unsigned integer variable 'i'. Due to type promotion, the negative value is interpreted as a very large positive integer, causing the subsequent loop to iterate excessively. This leads to memory corruption and ultimately results in a system crash. The root cause is a lack of proper error checking on the return value of get_sset_count() and the use of an unsigned integer type for a variable that should handle negative error codes. The fix involves adding error code checks and changing the variable 'i' to a signed integer type to correctly handle error returns and prevent out-of-bounds looping. This vulnerability affects Linux kernel versions prior to the patch and is relevant to systems using the DSA networking subsystem, which is common in embedded and networking devices running Linux. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, this vulnerability poses a risk primarily to systems running Linux kernels with the affected DSA networking code, including embedded devices, network appliances, and servers using this subsystem. Exploitation can lead to denial of service (DoS) through system crashes caused by memory corruption. While it does not directly lead to privilege escalation or remote code execution, the resulting instability can disrupt critical network infrastructure and services. This is particularly impactful for sectors relying on high availability such as telecommunications, financial services, and industrial control systems prevalent in Europe. Additionally, organizations using Linux-based network devices in their data centers or edge deployments may experience outages or degraded performance. The lack of known exploits reduces immediate risk, but the vulnerability's presence in widely deployed Linux kernels means that unpatched systems remain vulnerable to potential future exploitation or accidental crashes triggered by malformed network traffic or device misconfigurations.

European organizations should prioritize applying the official Linux kernel patches that address CVE-2021-47159 as soon as they become available. Specifically, updating to a kernel version where the get_sset_count() error handling is corrected will eliminate the vulnerability. Network administrators should audit their infrastructure to identify devices and systems using the DSA subsystem and verify kernel versions. For embedded or specialized devices where kernel upgrades are challenging, consider isolating affected devices from untrusted networks or applying network-level protections such as filtering malformed packets that could trigger the vulnerability. Monitoring system logs for unusual crashes or memory corruption symptoms related to the DSA driver can help detect exploitation attempts or accidental triggers. Additionally, organizations should implement robust backup and recovery procedures to minimize downtime in case of crashes. Engaging with Linux distribution vendors and device manufacturers to ensure timely patch deployment is also recommended.