[ CVE-2026-55736 · Published 23 Jun 2026 ]
Ash: Private action arguments can be set by user input via string-keyed params and atomic changesets
[ Why it matters ]Priority signals
- Public proof-of-concept exploit exists (CISA SSVC)
[ Description ]Official description
Improperly Controlled Modification of Dynamically-Determined Object Attributes vulnerability in ash-project ash allows a user to set the value of a private action argument that is intended to be controlled only by trusted server-side code. Action arguments declared with public?: false are meant to be set internally (for example via Ash.Changeset.set_private_argument/3) and must not be settable from end-user input. When a changeset is built from a parameter map, Ash filters out private arguments, but the filtering is incomplete. In the regular changeset path (for_create, for_update, for_destroy), private arguments are stripped only when the parameter key is an atom. When the key is a binary (string), as is the case for user-supplied parameters, the private argument is kept and the user controls its value. In the atomic path (Ash.Changeset.fully_atomic_changeset/4, also reached through atomic and bulk updates), private arguments are not stripped at all, regardless of whether the key is an atom or a binary. An attacker who can submit parameters to an action that defines a private argument can therefore inject a value for that argument. Depending on how the application uses the argument (for example an acting_user_id driving authorization or record ownership), this can lead to an integrity violation or privilege escalation. This issue affects ash: from 3.0.0 before 3.29.3.
[ Fixes ]Fixes and patches
- ash 3.29.3Fixed version · GitHub Advisories · erlang package ash: upgrade to 3.29.3 or later (affected >= 3.0.0, < 3.29.3)
[ Packages ]Affected open-source packages
- ash erlangAffected >= 3.0.0, < 3.29.3 · fixed in 3.29.3 · GHSA-f4hc-ppw9-4hhw