CVE-2024-47706 is a use-after-free (UAF) vulnerability in the Linux kernel's block I/O scheduler, specifically within the Budget Fair Queueing (BFQ) I/O scheduler implementation. The vulnerability arises due to improper handling of bfqq (BFQ queue) structures during merge operations between different BFQ I/O contexts (BICs). In the described scenario, multiple processes have their own BICs and associated bfqqs. When bfqqs are merged across these BICs, the kernel code incorrectly assigns ownership of bfqq structures, leading to a stale pointer reference. Specifically, after merging bfqq2 into bfqq3, the code mistakenly retains bfqq2's bic pointer as BIC1 (its initial owner) instead of updating it to reflect the new owner, BIC3. This results in a use-after-free condition when the kernel attempts to access or modify bfqq2, which may have already been freed or reallocated. The bug was detected by the Kernel Address Sanitizer (KASAN) during testing, showing slab-use-after-free errors in functions related to BFQ merge operations and queue handling. The root cause is a failure to check if a bfqq is part of a merge chain before assigning its bic pointer, leading to incorrect reference counting and premature freeing of memory. This vulnerability affects the Linux kernel version 6.6.0-07439-gba2303cacfda and potentially other versions with the same BFQ implementation. Exploitation would require triggering specific I/O patterns that cause bfqq merges across processes, which is complex but possible in multi-tenant or containerized environments. No known exploits are reported in the wild yet. The vulnerability could lead to kernel crashes, memory corruption, or privilege escalation if exploited, as use-after-free bugs in kernel space can be leveraged to execute arbitrary code or cause denial of service. The patch involves adding proper checks to verify if a bfqq is from a merge chain before assigning its bic pointer, preventing stale references and ensuring correct reference counting and memory management.

For European organizations, this vulnerability poses a significant risk to any systems running vulnerable Linux kernel versions with the BFQ I/O scheduler enabled. This includes servers, cloud infrastructure, and embedded devices widely used in industries such as finance, telecommunications, manufacturing, and government. Exploitation could lead to system instability, crashes, or potential privilege escalation, undermining confidentiality, integrity, and availability of critical services. Organizations relying on multi-tenant environments or container orchestration platforms are particularly at risk because the vulnerability involves interactions between processes and their I/O contexts. Disruption of critical infrastructure or data breaches could result from successful exploitation. Additionally, the complexity of the vulnerability and lack of public exploits may delay detection, increasing the window of exposure. The impact is heightened in sectors with stringent regulatory requirements for data protection and uptime, such as banking and healthcare, common across Europe. Furthermore, the vulnerability could be leveraged in targeted attacks against high-value assets, especially in countries with advanced digital infrastructure.

European organizations should prioritize updating their Linux kernels to versions that include the fix for CVE-2024-47706 as soon as patches become available from their Linux distribution vendors. Until patches are applied, organizations should consider disabling the BFQ I/O scheduler if feasible, switching to alternative schedulers like CFQ or deadline to reduce exposure. Monitoring kernel logs for KASAN or other memory corruption alerts can help detect exploitation attempts. Implement strict access controls and isolate critical workloads to minimize the risk of cross-process exploitation. Employ kernel hardening techniques such as Kernel Page Table Isolation (KPTI) and enable kernel lockdown features where supported. For containerized environments, enforce strict resource and namespace isolation to prevent malicious processes from triggering the vulnerability. Regularly audit and update all Linux-based systems, especially those exposed to untrusted users or network traffic. Collaborate with Linux distribution maintainers to receive timely security updates and verify patch deployment. Finally, conduct penetration testing and fuzzing focused on I/O scheduler behavior to proactively identify similar issues.