CVE-2026-118505

Improper Restriction of Excessive Authentication Attempts vulnerability in team-alembic ash_authentication allows an unauthenticated attacker to guess passwords and one-time passwords without limit.

The password, magic link and OTP strategies enforce brute_force_strategy by adding a preparation only to the actions they generate. When the resource defines one of those actions itself, the strategy uses it as written and nothing checked that it carried the preparation, so the setting compiled and applied no limit. The generators produce exactly this: mix ash_authentication.install writes sign_in_with_password, request_password_reset_token and request_magic_link, mix ash_authentication.upgrade then adds brute_force_strategy to those strategies, and mix ash_authentication.add_strategy.otp writes its OTP actions without the preparation. Separately, with registration_enabled? true the OTP sign-in is a create action, which preparations do not run on, so brute_force_strategy {:preparation, module} never applied to it.

This issue affects ash_authentication: from 5.0.0-rc.4 before 5.0.0-rc.16.

Improper Restriction of Excessive Authentication Attempts vulnerability in team-alembic ash_authentication allows an unauthenticated attacker to guess passwords and one-time passwords without limit.

The password, magic link and OTP strategies enforce brute_force_strategy by adding a preparation only to the actions they generate. When the resource defines one of those actions itself, the strategy uses it as written and nothing checked that it carried the preparation, so the setting compiled and applied no limit. The generators produce exactly this: mix ash_authentication.install writes sign_in_with_password, request_password_reset_token and request_magic_link, mix ash_authentication.upgrade then adds brute_force_strategy to those strategies, and mix ash_authentication.add_strategy.otp writes its OTP actions without the preparation. Separately, with registration_enabled? true the OTP sign-in is a create action, which preparations do not run on, so brute_force_strategy {:preparation, module} never applied to it.

This issue affects ash_authentication: from 5.0.0-rc.4 before 5.0.0-rc.16.

Improper Restriction of Excessive Authentication Attempts vulnerability in team-alembic ash_authentication allows an unauthenticated attacker to guess passwords and one-time passwords without limit.

The password, magic link and OTP strategies enforce brute_force_strategy by adding a preparation only to the actions they generate. When the resource defines one of those actions itself, the strategy uses it as written and nothing checked that it carried the preparation, so the setting compiled and applied no limit. The generators produce exactly this: mix ash_authentication.install writes sign_in_with_password, request_password_reset_token and request_magic_link, mix ash_authentication.upgrade then adds brute_force_strategy to those strategies, and mix ash_authentication.add_strategy.otp writes its OTP actions without the preparation. Separately, with registration_enabled? true the OTP sign-in is a create action, which preparations do not run on, so brute_force_strategy {:preparation, module} never applied to it.

This issue affects ash_authentication: from 5.0.0-rc.4 before 5.0.0-rc.16.

Improper Restriction of Excessive Authentication Attempts vulnerability in team-alembic ash_authentication allows an unauthenticated attacker to guess passwords and one-time passwords without limit.

The password, magic link and OTP strategies enforce brute_force_strategy by adding a preparation only to the actions they generate. When the resource defines one of those actions itself, the strategy uses it as written and nothing checked that it carried the preparation, so the setting compiled and applied no limit. The generators produce exactly this: mix ash_authentication.install writes sign_in_with_password, request_password_reset_token and request_magic_link, mix ash_authentication.upgrade then adds brute_force_strategy to those strategies, and mix ash_authentication.add_strategy.otp writes its OTP actions without the preparation. Separately, with registration_enabled? true the OTP sign-in is a create action, which preparations do not run on, so brute_force_strategy {:preparation, module} never applied to it.

This issue affects ash_authentication: from 5.0.0-rc.4 before 5.0.0-rc.16.

Summary

Improper Restriction of Excessive Authentication Attempts vulnerability in team-alembic ash_authentication allows an unauthenticated attacker to guess passwords and one-time passwords without limit.

The password, magic link and OTP strategies enforce brute_force_strategy by adding a preparation only to the actions they generate. When the resource defines one of those actions itself, the strategy uses it as written and nothing checked that it carried the preparation, so the setting compiled and applied no limit. The generators produce exactly this: mix ash_authentication.install writes sign_in_with_password, request_password_reset_token and request_magic_link, mix ash_authentication.upgrade then adds brute_force_strategy to those strategies, and mix ash_authentication.add_strategy.otp writes its OTP actions without the preparation. Separately, with registration_enabled? true the OTP sign-in is a create action, which preparations do not run on, so brute_force_strategy {:preparation, module} never applied to it.

This issue affects ash_authentication: from 5.0.0-rc.4 before 5.0.0-rc.16.

Workarounds

Add the brute-force preparation to each protected action defined on the resource, or remove the action so the strategy generates it. For brute_force_strategy {:audit_log, name} that is prepare {AshAuthentication.AddOn.AuditLog.IdentityBruteForcePreparation, action_name: <action>} on the password sign-in, password reset request, magic link request and OTP request actions, and prepare {AshAuthentication.AddOn.AuditLog.BruteForcePreparation, action_name: <action>} on a read OTP sign-in action. For {:preparation, MyModule} it is prepare MyModule. For OTP with registration_enabled? true, switch to brute_force_strategy :rate_limit.

Configurations

A password, magic link or OTP strategy sets brute_force_strategy and one of its protected actions (password sign-in, password reset request, magic link request, OTP sign-in or OTP request) is defined on the resource without the matching brute-force preparation, as on resources set up by the installer, the upgrade task or the OTP generator. Alternatively, an OTP strategy sets registration_enabled? true with brute_force_strategy {:preparation, module}. Actions the strategies generate themselves, and the OTP strategy's :rate_limit mode, are not affected.