CVE-2021-47153 is a vulnerability in the Linux kernel specifically affecting the i2c-i801 driver, which manages I2C bus communications on Intel hardware. The issue arises because the driver, after adding interrupt support, improperly handles interrupts triggered during a bus reset operation. When the driver attempts to recover from a timed-out transaction by setting the KILL bit, it inadvertently causes an interrupt. The interrupt handler (i801_isr) is not designed to handle interrupts generated in this context and mistakenly processes them as if they indicate the successful completion of a transaction. This misinterpretation can lead to an out-of-range memory access during block transactions, potentially causing kernel crashes or denial of service. The vulnerability was identified and reproduced multiple times by syzkaller, a kernel fuzzing tool, confirming its reliability and reproducibility. The fix implemented disables interrupts during the bus reset process, preventing the erroneous interrupt handling and restoring proper operation. This vulnerability requires local privileges with high-level permissions (PR:H) to exploit and does not require user interaction. The CVSS v3.1 score is 6.0, indicating a medium severity level, with a high impact on confidentiality and availability but no impact on integrity. The attack vector is local, and the complexity is low, but the attacker must have elevated privileges to exploit it. No known exploits are currently reported in the wild.

For European organizations, the impact of CVE-2021-47153 primarily concerns systems running Linux kernels with the vulnerable i2c-i801 driver enabled, especially on Intel-based hardware platforms. This vulnerability can lead to kernel crashes or denial of service conditions, potentially disrupting critical services or embedded systems relying on I2C communications. Industries such as manufacturing, telecommunications, and critical infrastructure that use Linux-based embedded devices or servers with Intel chipsets may experience operational interruptions. Confidentiality impact is high because out-of-range memory access could potentially be leveraged to read sensitive kernel memory, though no direct integrity impact is noted. The requirement for local high privileges limits remote exploitation, but insider threats or compromised accounts could exploit this vulnerability to escalate denial-of-service attacks or cause system instability. Given the widespread use of Linux in European IT environments, especially in servers and embedded devices, unpatched systems could face increased downtime and reliability issues, affecting business continuity and operational technology environments.

European organizations should prioritize updating their Linux kernel to versions that include the patch disabling interrupts during bus reset in the i2c-i801 driver. Specifically, kernel maintainers and system administrators should verify that their kernel versions incorporate the fix for CVE-2021-47153. For embedded and industrial Linux systems where kernel updates may be slower, consider implementing temporary mitigations such as disabling or limiting access to the i2c-i801 driver if feasible, or restricting local user privileges to prevent exploitation. Monitoring kernel logs for unusual i2c-i801 interrupt activity or bus reset failures can help detect attempted exploitation. Additionally, enforce strict access controls and audit local privileged accounts to reduce the risk of insider exploitation. Organizations should also engage with hardware and OS vendors to ensure timely patch deployment and validate that embedded devices receive firmware or kernel updates addressing this vulnerability. Finally, incorporate this vulnerability into vulnerability management and incident response plans to ensure rapid detection and remediation.