CVE-2025-37948 is a vulnerability identified in the Linux kernel specifically affecting the arm64 architecture's handling of classic Berkeley Packet Filter (cBPF) programs loaded via seccomp. The vulnerability arises from the ability of a malicious BPF program to manipulate the Branch History Buffer (BHB), a hardware feature used by modern CPUs to predict the flow of branch instructions for speculative execution. By influencing the branch history, an attacker can potentially affect the CPU's speculative execution behavior, which may lead to side-channel attacks or information leakage. To mitigate this, the Linux kernel update introduces a BHB mitigation sequence emitted at the epilogue (exit) of cBPF programs, effectively preventing the malicious manipulation of branch prediction state. This mitigation is applied only to classic cBPF programs loaded through seccomp, a Linux kernel feature used to restrict system calls for sandboxing purposes. The vulnerability does not currently have any known exploits in the wild, and no CVSS score has been assigned yet. The fix involves kernel-level changes to ensure that branch prediction state is sanitized upon exiting BPF programs, reducing the risk of speculative execution-based attacks that leverage branch history manipulation.

For European organizations, the impact of CVE-2025-37948 could be significant, particularly for those relying on Linux-based systems running on arm64 architecture, such as servers, embedded devices, and cloud infrastructure. Since seccomp and BPF are widely used for sandboxing and filtering system calls to enhance security, exploitation of this vulnerability could undermine these protections by enabling attackers to bypass security boundaries or leak sensitive information through speculative execution side channels. This could lead to unauthorized data disclosure, privilege escalation, or compromise of containerized environments and microservices that depend on seccomp filters. The impact is especially relevant for sectors with high security requirements such as finance, healthcare, telecommunications, and critical infrastructure. However, the absence of known exploits and the requirement for crafting malicious BPF programs limit immediate widespread exploitation. Nonetheless, the vulnerability poses a medium to high risk due to its potential to facilitate advanced side-channel attacks if exploited.

European organizations should prioritize updating their Linux kernels to versions that include the BHB mitigation for cBPF programs as soon as patches become available. Since the vulnerability specifically affects classic cBPF programs loaded via seccomp on arm64, organizations should audit their use of seccomp filters and BPF programs to identify any legacy or classic cBPF usage and consider migrating to more secure eBPF alternatives where feasible. Additionally, organizations should implement strict controls on who can load BPF programs, limiting this capability to trusted users and processes to reduce the attack surface. Monitoring and logging seccomp and BPF-related activities can help detect anomalous behavior indicative of exploitation attempts. For environments using container orchestration platforms like Kubernetes, ensure that runtime security policies restrict the use of untrusted BPF programs and enforce least privilege principles. Finally, maintain up-to-date threat intelligence feeds to stay informed about any emerging exploits targeting this vulnerability.