Ash stores :atom-typed attributes as strings and compares them as strings. When such an attribute is referenced in a filter, the comparison value is coerced through Ash.Type.Atom. Because the type defined no coerce/2 callback, coercion fell back to the default (cast_input/2), which calls String.to_atom/1 when the attribute is configured with the unsafe_to_atom?: true constraint.
Filtering such an attribute with attacker-controlled strings therefore interned a new, permanent atom for every distinct value. Atoms are never garbage collected and the BEAM caps the atom table, so an actor who can supply filter values for a public, filterable :atom attribute declared with unsafe_to_atom?: true can exhaust the atom table and crash the node (denial of service). AshPaperTrail is a notable example: its version resources expose a public, filterable version_action_name atom attribute with unsafe_to_atom?: true by default.
The fix adds a coerce/2 to Ash.Type.Atom that never interns atoms — a comparison value is left as a string, since the type is stored and compared as a string. Setting the attribute from action input (cast_input/2, which still honors unsafe_to_atom?) is unchanged.
This issue affects ash: from 3.5.1 before 3.34.3.
{
"cna_assigner": "EEF",
"cwe_ids": [
"CWE-770"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/94xxx/CVE-2026-94201.json"
}{
"extracted_events": [
{
"range": [
{
"introduced": "2970ba3bd5d36d6ad04c731ac87385375d457147"
},
{
"fixed": "5282f3f513053628cdd1bf2236ea22d975d934d4"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
},
{
"range": [
{
"introduced": "3.5.1"
},
{
"fixed": "3.34.3"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
},
{
"range": [
{
"fixed": "2970ba3bd5d36d6ad04c731ac87385375d457147"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "5282f3f513053628cdd1bf2236ea22d975d934d4"
}
],
"source": "REFERENCES_COMMIT"
}
]
}