CVE-2021-47027 is a vulnerability identified in the Linux kernel specifically affecting the mt76 wireless driver for the mt7921 chipset. The issue arises when the firmware required by the driver fails to download or is missing, which leads to a kernel crash. The crash is triggered by a kernel BUG in the function free_msi_irqs within the PCI MSI (Message Signaled Interrupts) handling code. The error trace shows that the kernel attempts to free MSI IRQ vectors during the PCI device probe process for the mt7921e driver, but due to the missing firmware, it encounters an invalid state causing a fatal exception and kernel panic. This vulnerability results in a denial of service (DoS) condition as the affected system crashes and stops functioning until rebooted. The problem is rooted in improper error handling when the firmware download fails, which should be gracefully managed but instead leads to a kernel panic. The vulnerability affects Linux kernel versions containing the mt7921 driver code prior to the fix. No public exploits are known at this time, and no CVSS score has been assigned. The vulnerability is relevant to systems using the mt7921 wireless chipset, commonly found in laptops and embedded devices running Linux. The issue is particularly critical in environments where system availability is paramount, as unexpected kernel panics can disrupt operations and cause data loss or service interruptions.

For European organizations, the impact of CVE-2021-47027 can be significant in sectors relying on Linux-based systems with mt7921 wireless hardware, such as enterprise laptops, embedded systems, or IoT devices. The kernel panic caused by this vulnerability results in a denial of service, potentially disrupting business operations, communications, and critical services. Organizations with large Linux deployments in office environments or industrial settings could face productivity losses and increased support costs due to system crashes. Additionally, the vulnerability could be exploited indirectly by causing firmware download failures (e.g., via network manipulation or supply chain issues), leading to widespread outages. While the vulnerability does not allow for privilege escalation or remote code execution, the loss of availability can impact confidentiality and integrity indirectly by interrupting security monitoring or patching processes. The lack of known exploits reduces immediate risk, but the vulnerability should be addressed proactively to maintain system stability and trustworthiness in critical infrastructure and enterprise environments.

To mitigate CVE-2021-47027, European organizations should: 1) Apply the latest Linux kernel updates that include the fix for the mt7921 driver to ensure proper handling of firmware download failures and prevent kernel panics. 2) Verify that firmware files for the mt7921 chipset are correctly installed and accessible on all affected systems to avoid triggering the bug. 3) Implement monitoring to detect kernel crashes and firmware loading errors promptly, enabling rapid response and remediation. 4) For critical systems, consider deploying fallback mechanisms or redundant wireless interfaces to maintain connectivity if the mt7921 device fails. 5) Conduct thorough testing of firmware updates and kernel patches in staging environments before production deployment to avoid unexpected disruptions. 6) Educate IT staff about this specific vulnerability and the importance of maintaining up-to-date firmware and kernel versions. 7) Limit user privileges to prevent unauthorized kernel module loading or firmware manipulation, reducing the risk of intentional exploitation. These targeted actions go beyond generic patching advice by focusing on firmware integrity, proactive monitoring, and operational continuity.