Null Pointer Dereference in Linux Kernel Affecting Shared Blocks

CVE-2026-31422

What is CVE-2026-31422?

A null pointer dereference vulnerability in the Linux kernel occurs when the flow_change function attempts to dereference a NULL pointer associated with shared blocks. Specifically, when flow filters are created without a fully qualified base class on these shared blocks, the lack of proper validation leads to a dereference of a NULL pointer, resulting in potential system instability. This vulnerability can be exploited when the function tcf_block_q dereferences the q->handle, which may not be initialized for shared blocks. Implementing a check with tcf_block_shared can prevent this dereference and appropriately handle shared block scenarios.

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