CVE-2026-45839

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> bpf: reject negative CO-RE accessor indices in bpf_core_parse_spec()<br /> <br /> CO-RE accessor strings are colon-separated indices that describe a path<br /> from a root BTF type to a target field, e.g. "0:1:2" walks through<br /> nested struct members. bpf_core_parse_spec() parses each component with<br /> sscanf("%d"), so negative values like -1 are silently accepted. The<br /> subsequent bounds checks (access_idx &gt;= btf_vlen(t)) only guard the<br /> upper bound and always pass for negative values because C integer<br /> promotion converts the __u16 btf_vlen result to int, making the<br /> comparison (int)(-1) &gt;= (int)(N) false for any positive N.<br /> <br /> When -1 reaches btf_member_bit_offset() it gets cast to u32 0xffffffff,<br /> producing an out-of-bounds read far past the members array. A crafted<br /> BPF program with a negative CO-RE accessor on any struct that exists in<br /> vmlinux BTF (e.g. task_struct) crashes the kernel deterministically<br /> during BPF_PROG_LOAD on any system with CONFIG_DEBUG_INFO_BTF=y<br /> (default on major distributions). The bug is reachable with CAP_BPF:<br /> <br /> BUG: unable to handle page fault for address: ffffed11818b6626<br /> #PF: supervisor read access in kernel mode<br /> #PF: error_code(0x0000) - not-present page<br /> Oops: Oops: 0000 [#1] SMP KASAN NOPTI<br /> CPU: 0 UID: 0 PID: 85 Comm: poc Not tainted 7.0.0-rc6 #18 PREEMPT(full)<br /> RIP: 0010:bpf_core_parse_spec (tools/lib/bpf/relo_core.c:354)<br /> RAX: 00000000ffffffff<br /> Call Trace:<br /> <br /> bpf_core_calc_relo_insn (tools/lib/bpf/relo_core.c:1321)<br /> bpf_core_apply (kernel/bpf/btf.c:9507)<br /> check_core_relo (kernel/bpf/verifier.c:19475)<br /> bpf_check (kernel/bpf/verifier.c:26031)<br /> bpf_prog_load (kernel/bpf/syscall.c:3089)<br /> __sys_bpf (kernel/bpf/syscall.c:6228)<br /> <br /> <br /> CO-RE accessor indices are inherently non-negative (struct member index,<br /> array element index, or enumerator index), so reject them immediately<br /> after parsing.