High [CVE-2026-74364] Reject exclusive maps as inner maps in map-in-map

In the Linux kernel, the following vulnerability has been resolved: bpf: Reject exclusive maps as inner maps in map-in-map An exclusive map (created with excl_prog_hash) is bound to a single program by hash: check_map_prog_compatibility() refuses to load any program whose digest does not match map->excl_prog_sha.

That check only runs for maps a program references directly, i.e. its used_maps.

A map reached at runtime through a map-of-maps is never in used_maps, and bpf_map_meta_equal() does not consider excl_prog_sha, so an exclusive map can be inserted into a non-exclusive outer map and then looked up and mutated by an unrelated program, bypassing the exclusivity guarantee.

For the signed loader this defeats the metadata map exclusivity check added in the signed loader: the cached map->sha[] is validated against the signed hash while another program on a hostile host rewrites the frozen map's contents through the outer map. A flaw was found in the Linux kernel's Berkeley Packet Filter (BPF) subsystem.

Exclusive maps, which are designed to be used by a single program, can be incorrectly inserted as inner maps within a map-in-map structure. This bypasses the intended security checks, allowing an unrelated program to modify the contents of an exclusive map.

Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat package: kernel.