CVE-2026-98063
UnknownSummary
In the Linux kernel, btf_var_show() unconditionally calls btf_type_id_resolve(), which dereferences btf->resolved_ids, which is NULL for a base BTF (e.g., vmlinux BTF). A BPF program passing a BTF_KIND_VAR type_id from vmlinux BTF to bpf_snprintf_btf() triggers a NULL dereference. The fix resolves the var's type directly with btf_type_skip_modifiers() when resolved_ids is NULL.
Risk Assessment
A local attacker with CAP_BPF privileges can trigger a kernel crash (null-ptr-deref) via bpf_snprintf_btf(), causing denial of service or potential privilege escalation. The risk is significant in systems with BPF access.
Recommendation
Update the Linux kernel to a version with the fix. Restrict BPF program loading 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 in btf_var_show() btf_var_show() calls btf_type_id_resolve() unconditionally, which dereferences btf->resolved_ids. That is NULL for a base BTF - e.g. the vmlinux BTF that bpf_snprintf_btf() renders against - since base BTF is not resolved during parsing. btf_modifier_show() guards this with 'if (btf->resolved_ids)', but btf_var_show() does not. A BPF program that passes the type_id of a BTF_KIND_VAR from the vmlinux BTF to bpf_snprintf_btf() thus NULL-derefs: KASAN: probably user-memory-access in range [0x46638-0x4663f] RIP: 0010:btf_var_show (kernel/bpf/btf.c:2929) Call Trace: <TASK> btf_type_show (kernel/bpf/btf.c:8259) btf_type_snprintf_show (kernel/bpf/btf.c:8329) 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:84) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) </TASK> Resolve the var's type directly with btf_type_skip_modifiers() when resolved_ids is NULL, mirroring btf_modifier_show().
Vulnerability data from NVD (NIST) · CISA KEV · EPSS