Quinn Wilton

**Name of the Vulnerable Software and Affected Versions** ash versions 3.5.1 through 3.34.2 **Description** Ash stores `:atom`-typed attributes as strings and compares them as strings. When such an attribute is used in a filter, the comparison value is processed through `Ash.Type.Atom`. Due to the absence of a `coerce/2` callback, the process defaults to `cast input/2`, which invokes `String.to atom/1` when the attribute is configured with the `unsafe to atom?: true` constraint. An attacker providing distinct strings to a public, filterable `:atom` attribute with this constraint can cause the system to intern a new, permanent atom for every value. Since atoms are not garbage collected and the BEAM (the Erlang Virtual Machine) has a limited atom table, this can lead to atom table exhaustion and a denial of service crash. This is reachable when an application exposes such an attribute via interfaces like AshGraphql, AshJsonApi, or the `filter input/2` function. AshPaperTrail is an example of a library that exposes the `version action name` attribute with this configuration by default. **Recommendations** Update ash to version 3.34.3 or later. As a temporary mitigation, avoid using the `unsafe to atom?: true` constraint on public, filterable `:atom` attributes.