In the Linux kernel, the following vulnerability has been resolved:
selinux: require every boolean value to be defined
p_bools.nprim comes from the policy image independently of how many booleans follow it, and cond_index_bool() fills bool_val_to_struct[] at value - 1, so a count larger than the values present leaves NULL entries. Every user of that array then walks it by index and dereferences each entry: cond_evaluate_expr() on the access-vector path, security_get_bools() and security_get_bool_value() behind selinuxfs, and security_set_bools(). A sparse class value is absorbed by policydb_class_isvalid() and its siblings; booleans have no such predicate, and no consumer that could use one.
Reject a boolean value that no boolean defines, once, where the array is built. Conforming policies define every boolean they declare and are unaffected.