---
id: CVE-2026-94201
title: 'Ash stores :atom-typed attributes as strings and compares them as strings'
summary: >-
  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 f…
severity: high
cvss: 8.2
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'
cwe:
  - CWE-770
vendor: ash-project
product: ash
affected:
  - ash >= 3.5.1 < 3.34.3
  - >-
    ash-project/ash >= 2970ba3bd5d36d6ad04c731ac87385375d457147 <
    5282f3f513053628cdd1bf2236ea22d975d934d4
published: '2026-10-05'
updated: '2026-10-05'
sourceUpdated: '2026-10-05T20:17:28.693'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-94201'
references:
  - url: 'https://cna.erlef.org/cves/CVE-2026-94201.html'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/ash-project/ash/commit/2970ba3bd5d36d6ad04c731ac87385375d457147
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/ash-project/ash/commit/5282f3f513053628cdd1bf2236ea22d975d934d4
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-94201'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
tags:
  - nvd
  - cve.org
cvssSource: cna
ingestedAt: '2026-10-05T20:32:56.656Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.