Linux Kernel prior 7.1.5/7.2-rc1 BPF bpf_obj_free_fields use after free

Summaryinfo

A vulnerability described as very critical has been identified in Linux Kernel. This issue affects the function bpf_obj_free_fields of the component BPF. Executing a manipulation can lead to use after free. This vulnerability is tracked as CVE-2026-74314. The attack is restricted to local execution. No exploit exists.

Detailsinfo

A vulnerability has been found in Linux Kernel and classified as very critical. This vulnerability affects the function bpf_obj_free_fields of the component BPF. The manipulation with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at git.kernel.org. This vulnerability was named CVE-2026-74314 since 08/15/2026. The exploitation appears to be easy. Local access is required to approach this attack. Additional levels of successful authentication are required for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 08/15/2026).

Upgrading to version 7.1.5 or 7.2-rc1 eliminates this vulnerability. Applying the patch 9ea734e2cc0143d7429ab7dc0b20c85e5836183c/a3a81d247651218e47153f2d2afd7aee236726fd is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

License

• open-source

Website

• Vendor: https://www.kernel.org/

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