CVE-2026-74314
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
A vulnerability in the Linux kernel's BPF mechanism related to map value recycling has been discovered. During map update or delete, special fields (e.g., timers, workqueues) were freed in the operation context, which could be unsafe in NMI context. A new cancel function has been introduced that performs only NMI-safe cleanup, leaving full destruction to the final cleanup path.
Risk Assessment
Organizations may face incorrect behavior of BPF programs that rely on immediate freeing of special fields after map update/delete. This could lead to logic errors, resource leaks, or potential system stability issues, especially in environments using BPF for monitoring or security.
Recommendation
It is recommended to update the Linux kernel to a version containing the fix for CVE-2026-74314 as soon as possible. Also, review BPF programs for dependencies on eager freeing of special fields and adjust them to the new, relaxed semantics.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: bpf: Cancel special fields on map value recycle Map update and delete paths currently call bpf_obj_free_fields() when a value is being replaced or recycled. That makes field destruction depend on the context of the update/delete operation. For tracing programs this can include NMI context, where referenced kptr destructors, uptr unpinning, and graph root destruction are not generally safe. Introduce bpf_obj_cancel_fields() for the reusable-value path. It only performs NMI-safe cleanup for timer, workqueue, and task_work fields. Fields that need full destruction are left attached to the recycled value and are destroyed by the final cleanup path instead. Switch array and hashtab update/delete/recycle paths to this cancel helper. Keep bpf_obj_free_fields() for final map destruction and for bpf_mem_alloc destructors. Preallocated hashtabs do not have allocator destructors, so teardown continues to walk the normal and extra elements and fully destroy their fields. This deliberately relaxes the eager-free semantics of map update/delete for special fields. Programs that relied on a recycled map slot becoming empty immediately after update/delete were relying on behavior that cannot be implemented safely from every BPF execution context without offloading arbitrary destructors. There is a chance this change breaks programs making assumptions regarding the eager freeing of fields. If so, we can relax semantics to cancellation only when irqs_disabled() is true in the future. However, theoretically, map values that get reused eagerly already have weaker guarantees as parallel users can recreate freed fields before the new element becomes visible again.