Reachable only when an application uses Ash.Policy.Authorizer field policies to restrict a calculation or aggregate, and exposes filtering on it to an actor who is denied that field (for example an authenticated user filtering through AshGraphql or AshJsonApi).
Ash field_policies are documented to protect against filter-based information disclosure: when a field the actor may not see is referenced in a filter, it is replaced with an expression that evaluates to nil, so a filter cannot be used as a yes/no oracle to read a value the actor cannot see.
This nilling was applied to attributes but not to calculations or aggregates. A user-supplied filter reference to a calculation or aggregate carries an Ash.Query.Calculation / Ash.Query.Aggregate struct, which the authorizer's reference replacement did not match (it only matched the Ash.Resource.* structs), so the filter ran against the real value.
As a result, an actor whose field policies forbid a calculation or aggregate can still filter by it (for example filter(secret_calc == \"x\") or filter(comment_count == n)) and learn the value from whether rows match — an oracle that recovers field-policy-protected values one probe at a time. Filtering is commonly exposed to lower-privileged actors (for example via AshGraphql or AshJsonApi filter arguments), which is exactly the surface field policies are meant to protect.
The fix routes filter references to calculations and aggregates through the same field-policy nilling as attributes.
\nThis issue affects ash: from 2.11.0-rc.0 before 3.33.4.
"},{"base64":false,"type":"text/markdown","value":"Ash `field_policies` are documented to protect against filter-based information disclosure: when a field the actor may not see is referenced in a filter, it is replaced with an expression that evaluates to `nil`, so a filter cannot be used as a yes/no oracle to read a value the actor cannot see.\n\nThis nilling was applied to attributes but not to calculations or aggregates. A user-supplied filter reference to a calculation or aggregate carries an `Ash.Query.Calculation` / `Ash.Query.Aggregate` struct, which the authorizer's reference replacement did not match (it only matched the `Ash.Resource.*` structs), so the filter ran against the real value.\n\nAs a result, an actor whose field policies forbid a calculation or aggregate can still filter by it (for example `filter(secret_calc == \"x\")` or `filter(comment_count == n)`) and learn the value from whether rows match — an oracle that recovers field-policy-protected values one probe at a time. Filtering is commonly exposed to lower-privileged actors (for example via AshGraphql or AshJsonApi filter arguments), which is exactly the surface field policies are meant to protect.\n\nThe fix routes filter references to calculations and aggregates through the same field-policy nilling as attributes.\n\nThis issue affects ash: from 2.11.0-rc.0 before 3.33.4."}],"value":"Ash field_policies are documented to protect against filter-based information disclosure: when a field the actor may not see is referenced in a filter, it is replaced with an expression that evaluates to nil, so a filter cannot be used as a yes/no oracle to read a value the actor cannot see.\n\nThis nilling was applied to attributes but not to calculations or aggregates. A user-supplied filter reference to a calculation or aggregate carries an Ash.Query.Calculation / Ash.Query.Aggregate struct, which the authorizer's reference replacement did not match (it only matched the Ash.Resource.* structs), so the filter ran against the real value.\n\nAs a result, an actor whose field policies forbid a calculation or aggregate can still filter by it (for example filter(secret_calc == \"x\") or filter(comment_count == n)) and learn the value from whether rows match — an oracle that recovers field-policy-protected values one probe at a time. Filtering is commonly exposed to lower-privileged actors (for example via AshGraphql or AshJsonApi filter arguments), which is exactly the surface field policies are meant to protect.\n\nThe fix routes filter references to calculations and aggregates through the same field-policy nilling as attributes.\n\nThis issue affects ash: from 2.11.0-rc.0 before 3.33.4."}],"impacts":[{"capecId":"CAPEC-1","descriptions":[{"lang":"en","value":"CAPEC-1 Accessing Functionality Not Properly Constrained by ACLs"}]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":6,"baseSeverity":"MEDIUM","privilegesRequired":"LOW","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1220","description":"CWE-1220 Insufficient Granularity of Access Control","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-09-16T08:28:44.114Z","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","shortName":"EEF"},"references":[{"name":"GHSA-7qr8-wrvq-566q","tags":["vendor-advisory"],"url":"https://github.com/ash-project/ash/security/advisories/GHSA-7qr8-wrvq-566q"},{"name":"EEF CNA record for CVE-2026-86338","tags":["related"],"url":"https://cna.erlef.org/cves/CVE-2026-86338.html"},{"name":"OSV record EEF-CVE-2026-86338","tags":["related"],"url":"https://osv.dev/vulnerability/EEF-CVE-2026-86338"},{"name":"Introducing commit 0b6d93c in ash-project/ash","tags":["related"],"url":"https://github.com/ash-project/ash/commit/0b6d93c7c4637280b46ae66ea1d2eaf013701238"},{"name":"Fix commit b3d4503 in ash-project/ash","tags":["patch"],"url":"https://github.com/ash-project/ash/commit/b3d4503241f3deacb5ceb955e10a4fa927da0f67"}],"source":{"discovery":"EXTERNAL"},"title":"Ash field policies do not filter-nil forbidden calculations and aggregates, enabling an information-disclosure oracle"}},"cveMetadata":{"assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","assignerShortName":"EEF","cveId":"CVE-2026-86338","datePublished":"2026-09-16T08:28:44.114Z","dateReserved":"2026-09-15T15:30:01.895Z","dateUpdated":"2026-09-16T08:28:44.114Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"}