CVE-2025-48044

### Summary Bypass policies incorrectly authorize requests when their condition evaluates to true but their authorization checks fail and no other policies apply. ### Impact Resources with bypass policies can be accessed without proper authorization when: - Bypass condition evaluates to true - Bypass authorization checks fail - Other policies exist but their conditions don't match ### Details Vulnerable code in: [lib/ash/policy/policy.ex:69](https://github.com/ash-project/ash/blob/b2e4d625/lib/ash/policy/policy.ex#L69) ```elixir {%{bypass?: true}, cond_expr, complete_expr}, {one_condition_matches, all_policies_match} -> { b(cond_expr or one_condition_matches), # <- Bug: uses condition only b(complete_expr or all_policies_match) } ``` The final authorization decision is: `one_condition_matches AND all_policies_match` When a bypass condition is true but bypass policies fail, and subsequent policies have non-matching conditions: 1. **one_condition_matches** = `cond_expr` (bypass condition) = **true** (bug - should check if bypass actually authorizes) 2. **all_policies_match** = `(complete_expr OR NOT cond_expr)` for each policy - For non-matching policies: `(false OR NOT false)` = **true** (policies don't apply) 3. **Final**: `true AND true` = **true** (incorrectly authorized) The bypass condition alone satisfies "at least one policy applies" even though the bypass fails to authorize. ### Fix Replace `cond_expr` with `complete_expr` on line 69: ```elixir {%{bypass?: true}, _cond_expr, complete_expr}, {one_condition_matches, all_policies_match} -> { b(complete_expr or one_condition_matches), # <- Fixed b(complete_expr or all_policies_match) } ``` Line 52 should also be updated for consistency (though it's only triggered when bypass is the last policy, making it coincidentally safe in practice): ```elixir {%{bypass?: true}, _cond_expr, complete_expr}, {one_condition_matches, true} -> { b(complete_expr or one_condition_matches), # <- For consistency complete_expr } ``` ### PoC ```elixir policies do bypass always() do authorize_if actor_attribute_equals(:is_admin, true) end policy action_type(:read) do authorize_if always() end end ``` Non-admin user can perform create actions (should be denied). Test demonstrating the bug: ```elixir test "bypass policy bug" do policies = [ %Ash.Policy.Policy{ bypass?: true, condition: [{Ash.Policy.Check.Static, result: true}], # condition = true policies: [ %Ash.Policy.Check{ type: :authorize_if, check: {Ash.Policy.Check.Static, result: false}, # policies = false check_module: Ash.Policy.Check.Static, check_opts: [result: false] } ] }, %Ash.Policy.Policy{ bypass?: false, condition: [{Ash.Policy.Check.Static, result: false}], policies: [ %Ash.Policy.Check{ type: :authorize_if, check: {Ash.Policy.Check.Static, result: true}, check_module: Ash.Policy.Check.Static, check_opts: [result: true] } ] } ] expression = Ash.Policy.Policy.expression(policies, %{}) assert expression == false # Expected: false (deny) # Actual on main: true (incorrectly authorized) end ```

## Summary Incorrect Authorization vulnerability in ash-project ash allows Authentication Bypass. This issue affects ash: from 3.6.3 before 3.7.1.