CVE-2021-47540 is a vulnerability identified in the Linux kernel, specifically within the mt76 wireless driver for MediaTek chipsets, targeting the mt7915 device. The flaw is a NULL pointer dereference occurring in the function mt7915_get_phy_mode, which is invoked when adding an IBSS (Independent Basic Service Set) interface to the mt7915 driver. IBSS mode is used for ad-hoc wireless networking without an access point. The vulnerability manifests when the driver attempts to handle IBSS network creation or joining, leading to a kernel NULL pointer dereference and consequent kernel panic or system crash. The detailed kernel logs indicate that the fault occurs due to dereferencing a NULL pointer at address 0x0 during the execution of mt7915_get_phy_mode, triggered by ieee80211 stack operations related to IBSS interface management. This vulnerability can cause denial of service (DoS) by crashing the kernel, impacting system availability. The issue affects Linux kernel versions containing the vulnerable mt7915 driver code prior to the patch. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability requires the system to be running the affected MediaTek mt7915 wireless chipset and to be operating or attempting to operate in IBSS mode, which is less common than infrastructure mode but still relevant in certain wireless networking scenarios.

For European organizations, the primary impact of CVE-2021-47540 is the potential for denial of service on Linux systems using MediaTek mt7915 wireless chipsets when operating in IBSS mode. This could disrupt wireless connectivity and cause system instability or crashes, particularly in environments relying on ad-hoc wireless networks for communication or specialized industrial or embedded applications. While the vulnerability does not directly lead to privilege escalation or data leakage, the forced kernel panic can interrupt critical services, affecting operational continuity. Organizations using Linux-based devices with mt7915 wireless hardware in sectors such as telecommunications, manufacturing, or IoT deployments may face increased risk. The lack of known exploits reduces immediate threat but does not eliminate the risk of future weaponization. The vulnerability’s impact is limited to systems with the specific hardware and configuration, so widespread impact is unlikely but targeted attacks or accidental triggers could cause localized outages.

To mitigate CVE-2021-47540, European organizations should: 1) Apply the latest Linux kernel updates that include the patch fixing the NULL pointer dereference in the mt7915 driver. Since no patch links are provided, monitoring official Linux kernel repositories and distributions for updates is critical. 2) Disable IBSS mode on affected devices if it is not required, as the vulnerability is triggered specifically during IBSS interface creation or joining. 3) For embedded or specialized devices using the mt7915 chipset, coordinate with hardware vendors or device manufacturers to obtain firmware or driver updates addressing this issue. 4) Implement monitoring for kernel crashes or wireless interface errors related to mt7915 to detect potential exploitation or accidental triggers. 5) Consider network segmentation and limiting wireless interface usage to infrastructure mode to reduce exposure. 6) Maintain robust incident response procedures to quickly recover from potential denial of service events caused by this vulnerability.