CVE-2024-50047 is a use-after-free (UAF) vulnerability identified in the Linux kernel's SMB client implementation, specifically affecting the asynchronous decryption process used during large read operations over CIFS/SMB shares. The vulnerability arises from improper handling of the AEAD (Authenticated Encryption with Associated Data) transform (TFM) objects in the crypto API when performing asynchronous decryption. In the affected code, the same TFM is used concurrently for asynchronous operations, leading to a race condition where the memory associated with the TFM can be freed while still in use, causing a slab-use-after-free error. This can result in kernel crashes (denial of service) or potentially allow attackers to execute arbitrary code or escalate privileges if exploited further. The issue manifests when mounting SMB shares with specific options (e.g., seal and esize=1) and reading large files, triggering the asynchronous decryption path. The fix involves allocating a separate AEAD TFM for asynchronous decryption to avoid concurrent use of the same object, and removing unnecessary callback and wait calls since the operation is effectively synchronous. This vulnerability affects Linux kernel versions prior to the patch and is particularly relevant for systems using CIFS/SMB clients with encryption enabled. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet.

For European organizations, this vulnerability poses a significant risk primarily to servers and endpoints running Linux with SMB client functionality enabled, especially those accessing encrypted SMB shares. The impact includes potential kernel crashes leading to denial of service, which can disrupt critical file-sharing services and business operations. In more severe scenarios, exploitation could allow attackers to execute arbitrary code with kernel privileges, compromising system confidentiality and integrity. Organizations relying on Linux-based file servers, virtualization hosts, or cloud infrastructure that mount SMB shares are at heightened risk. Given the widespread use of Linux in enterprise environments across Europe, including government, finance, and industrial sectors, the vulnerability could affect a broad range of critical infrastructure. Additionally, the use of encrypted SMB traffic is common in environments requiring secure file transfers, increasing the attack surface. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits targeting this flaw.

European organizations should promptly apply the official Linux kernel patches that address CVE-2024-50047 once available from their Linux distribution vendors. Until patches are deployed, organizations should consider the following mitigations: 1) Disable SMB encryption (seal) on CIFS mounts if feasible, to avoid triggering the vulnerable async decryption path; 2) Limit access to SMB shares from untrusted networks to reduce exposure; 3) Monitor kernel logs for signs of slab-use-after-free errors or crashes related to CIFS/SMB client operations; 4) Employ kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in testing environments to detect similar issues proactively; 5) Use network segmentation and strict firewall rules to restrict SMB traffic; 6) Regularly update Linux kernels and related packages to incorporate security fixes; 7) For virtualized environments, ensure hypervisor and guest OS kernels are patched to prevent cascading failures. These steps go beyond generic advice by focusing on SMB encryption settings and kernel-level monitoring specific to this vulnerability.