CVE-2026-98064
UnknownSummary
In the Linux kernel, btf_modifier_show() unconditionally calls show() for the resolved type, but for the void type (type_id 0, BTF_KIND_UNKN) there is no entry in kind_ops[], so the show pointer is NULL. A BPF program passing a "const void" type_id from vmlinux BTF to bpf_snprintf_btf() triggers a NULL dereference. The fix falls back to btf_df_show() with the "<unsupported kind:N>" placeholder.
Risk Assessment
A local attacker with CAP_BPF privileges can trigger a kernel crash (null-ptr-deref) via bpf_snprintf_btf(), leading to denial of service or potential privilege escalation. In environments with unprivileged BPF, the risk is significant.
Recommendation
Update the Linux kernel to a version containing the fix for this CVE. Restrict BPF access (CAP_BPF) to trusted users until the update is applied.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix NULL-ptr-deref when showing a void BTF type btf_modifier_show() resolves the modifier and then calls btf_type_ops(t)->show() unconditionally. For the void type (type_id 0, BTF_KIND_UNKN) kind_ops[] has no entry, so ->show is NULL. A "const void" (a modifier resolving to void) cannot be a map key or value - map_check_btf() rejects it because void has no size - so the map dump path does not reach it. But bpf_snprintf_btf() takes a type_id straight from the BPF program, and passing such a "const void" from the vmlinux BTF NULL-derefs: KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] RIP: 0010:btf_modifier_show (kernel/bpf/btf.c:2914) Call Trace: <TASK> btf_type_show (kernel/bpf/btf.c:8251) btf_type_snprintf_show (kernel/bpf/btf.c:8321) bpf_snprintf_btf (kernel/trace/bpf_trace.c:1047) bpf_prog_test_run_raw_tp (net/bpf/test_run.c:829) __sys_bpf (kernel/bpf/syscall.c:4804) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) </TASK> Fall back to btf_df_show() when the resolved type has no show op; it emits the "<unsupported kind:N>" placeholder already used for kinds like FWD and FUNC. bpf_snprintf_btf() then returns the length as usual.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS