An action must declare a private argument (one defined with public?: false) whose value is meant to be set only by trusted server-side code, and the application must build the changeset from untrusted user-supplied parameters, passing them straight into Ash.Changeset.for_create/3, for_update/3, for_destroy/3, or into an atomic or bulk update.
"}],"value":"An action must declare a private argument (one defined with public?: false) whose value is meant to be set only by trusted server-side code, and the application must build the changeset from untrusted user-supplied parameters, passing them straight into Ash.Changeset.for_create/3, for_update/3, for_destroy/3, or into an atomic or bulk update."}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:ash-project:ash:*:*:*:*:*:*:*:*","versionEndExcluding":"3.29.3","versionStartIncluding":"3.0.0","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"AND"}],"credits":[{"lang":"en","type":"finder","value":"Alfred Vié"},{"lang":"en","type":"remediation reviewer","value":"Zach Daniel"},{"lang":"en","type":"analyst","value":"Jonatan Männchen / EEF"}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"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.
"}],"value":"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.\n\nAction 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.\n\nIn 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.\n\nAn 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.\n\nThis issue affects ash: from 3.0.0 before 3.29.3."}],"impacts":[{"capecId":"CAPEC-77","descriptions":[{"lang":"en","value":"CAPEC-77 Manipulating User-Controlled Variables"}]}],"metrics":[{"cvssV4_0":{"attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"LOCAL","baseScore":5.9,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","vectorString":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-915","description":"CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-06-23T18:21:13.033Z","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","shortName":"EEF"},"references":[{"tags":["vendor-advisory","related"],"url":"https://github.com/ash-project/ash/security/advisories/GHSA-f4hc-ppw9-4hhw"},{"tags":["related"],"url":"https://cna.erlef.org/cves/CVE-2026-55736.html"},{"tags":["related"],"url":"https://osv.dev/vulnerability/EEF-CVE-2026-55736"},{"tags":["patch"],"url":"https://github.com/ash-project/ash/commit/d9b3100219b3ea86d73202bf7368c03a7688efea"}],"source":{"discovery":"EXTERNAL"},"title":"Private action arguments can be set by user input in Ash","x_generator":{"engine":"cvelib 1.8.0"}}},"cveMetadata":{"assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","assignerShortName":"EEF","cveId":"CVE-2026-55736","datePublished":"2026-06-23T18:21:13.033Z","dateReserved":"2026-06-17T10:44:34.365Z","dateUpdated":"2026-06-23T18:21:13.033Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"}