Medium [CVE-2026-64354] Validate BTF repeated field counts before expansion

In the Linux kernel, the following vulnerability has been resolved: bpf: Validate BTF repeated field counts before expansion btf_parse_struct_metas() walks user-supplied BTF during BPF_BTF_LOAD, and btf_repeat_fields() expands repeatable fields from array elements into the fixed BTF_FIELDS_MAX scratch array used by btf_parse_fields().

The remaining-capacity check performs the expanded field count calculation in u32. The following memcpy() can then write past the end of the array.

Use checked addition and multiplication before copying repeated fields and reject impossible counts. A flaw was found in the Linux kernel's BPF (Berkeley Packet Filter) component.

This vulnerability, located in the `btf_repeat_fields()` function, is caused by an integer overflow when processing user-supplied BPF Type Format (BTF) data. A local attacker could exploit this flaw by providing a specially crafted BTF, leading to a heap out-of-bounds write.

This could result in privilege escalation, allowing the attacker to gain elevated access to the system. The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl.

This would require a privileged user with CAP_SYS_ADMIN or root to be able to abuse this flaw reducing its attack space.