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CVE-2025-40123 is a Linux kernel BPF flaw caused by failure to enforce expected_attach_type compatibility when populating or using BPF tail-call maps. BPF programs with the same base program type but incompatible expected attachment types could be chained by a tail call, bypassing attach-type-specific validation, access restrictions, and helper-function constraints. In the reported XDP case, an entry program tail-calls into a program validated for a device-map attachment context; execution then occurs without the context required for access to an XDP buffer transmit-queue member, resulting in an uninitialized pointer condition and NULL pointer dereference in bpf_prog_test_run_xdp(). Similar constraint violations can affect other program types whose permitted accesses or helper functions depend on expected_attach_type. The fix adds expected_attach_type validation to __bpf_prog_map_compatible() for tail-call maps. Device-map and CPU-map execution paths are excluded because they establish a new execution context.
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A Linux kernel BPF vulnerability allows tail calls between programs with incompatible expected_attach_type values, violating context-specific access and functionality restrictions. The reported XDP case causes a NULL pointer dereference; related compatibility problems also affect BPF_PROG_TYPE_CGROUP_SOCK_ADDR programs. The fix enforces expected_attach_type compatibility for tail-call maps in __bpf_prog_map_compatible(). The reference assigns a CVSS v3 base score of 7.8.
A high-impact local vulnerability affecting Unity Linux systems. Exploitation requires local access and low privileges, requires no user interaction, and can result in high confidentiality, integrity, and availability impact.
A Linux kernel BPF subsystem vulnerability involving improper enforcement of expected_attach_type for tailcall compatibility, enabling an uninitialized pointer issue that can lead to a NULL pointer dereference.
A Linux kernel BPF subsystem vulnerability in tail-call compatibility validation. BPF programs with incompatible expected_attach_type values could be chained through tail-call maps, bypassing attach-type-specific access and helper restrictions and, in the demonstrated XDP case, causing an uninitialized-pointer condition and NULL-pointer dereference.
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