CVE-2024-50253 is a vulnerability identified in the Linux kernel's BPF (Berkeley Packet Filter) subsystem, specifically within the function bpf_iter_bits_new(). The vulnerability arises from insufficient validation of the parameter nr_words, which represents the number of words to be processed. Without proper validation, an attacker can supply a value for nr_words that causes an integer multiplication overflow when calculating nr_bits (the total number of bits). For example, if nr_words is set to 0x04000001, the multiplication overflows and nr_bits becomes 64 instead of the expected larger value. This overflow leads to an incorrect calculation of nr_bytes used in the bpf_probe_read_kernel_common() function, potentially causing stack corruption due to reading or writing beyond the intended memory boundaries. The root cause is the lack of a boundary check on nr_words, allowing values that exceed the safe limits of the BPF memory allocator. The fix implemented limits nr_words to a maximum of 511, which aligns with the current BPF memory allocator constraints. Additionally, the patch introduces the use of the helper function bpf_mem_alloc_check_size() to dynamically verify if nr_bytes is too large, returning an error code (-E2BIG) for oversized allocations instead of -ENOMEM. This approach ensures future compatibility if the allocator's size limits change. This vulnerability could be exploited by a local attacker with the ability to load or manipulate BPF programs, potentially leading to stack corruption and undefined behavior in the kernel, which might be leveraged for privilege escalation or denial of service. No known exploits are currently reported in the wild, and the vulnerability was published on November 9, 2024.

For European organizations, this vulnerability poses a significant risk primarily to systems running vulnerable Linux kernel versions that support BPF functionality. Since Linux is widely used across European enterprises, government institutions, and critical infrastructure, the potential for exploitation could lead to kernel-level memory corruption. This may result in system crashes (denial of service) or, more critically, privilege escalation attacks where an attacker gains unauthorized root-level access. Such escalations could compromise sensitive data confidentiality and integrity, disrupt business operations, and impact availability of critical services. Organizations relying on Linux-based servers, cloud infrastructure, or embedded devices with BPF capabilities are particularly at risk. The absence of known exploits currently reduces immediate threat but does not eliminate the risk, especially as attackers may develop exploits following public disclosure. The impact is heightened in environments where untrusted users have the ability to load or interact with BPF programs, such as multi-tenant cloud platforms or shared hosting environments common in Europe. Additionally, critical sectors like finance, healthcare, and public administration, which heavily depend on Linux servers, could face severe operational and reputational damage if exploited.

European organizations should promptly apply the official Linux kernel patches that address CVE-2024-50253 once available from their Linux distribution vendors. Until patches are applied, organizations should restrict access to BPF program loading capabilities to trusted users only, using Linux security modules (e.g., SELinux, AppArmor) and kernel lockdown features where possible. Monitoring and auditing BPF-related system calls and kernel logs can help detect suspicious activity. Employing kernel hardening techniques such as enabling kernel address space layout randomization (KASLR) and stack protection can reduce exploitation likelihood. For cloud environments, enforce strict tenant isolation and limit capabilities that allow BPF program loading. Organizations should also review and update their incident response plans to include potential kernel-level exploits. Regularly updating Linux kernels and subscribing to security advisories from vendors and the Linux community will ensure timely awareness and remediation of such vulnerabilities. Finally, consider disabling BPF functionality entirely if it is not required for operational needs, as a temporary risk reduction measure.