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Description

Incorrect Authorization vulnerability in ash-project ash_typescript allows an unauthorized RPC caller to read attribute values that Ash field policies denied.

When a field policy denies an attribute, Ash substitutes %Ash.ForbiddenField{}, which retains the real value in original_value because embedded resources must remain writable, and hides it from Inspect rather than removing it. AshTypescript.Rpc.ResultProcessor strips these markers to nil on its template-driven paths, but normalize_primitive/1 in lib/ash_typescript/rpc/result_processor.ex had no such clause, so a marker fell through to the generic struct branch which calls Map.from_struct/1 and serializes every key, original_value included. The denied value is returned to the caller inside the marker that represents its own denial.

The simplest trigger is an action returning an embedded resource as a map, which routes through normalize_resource_struct/2 with an empty template. normalize_value_for_json/1 is a public, unguarded entry point to the same path.

This issue affects ash_typescript: from 0.11.0 before 0.18.0.

Weaknesses & attack patterns

Weakness

CWE-863 · Incorrect Authorization in catalog → MITRE ↗

Attack patterns

CAPEC-122 · Privilege Abuse MITRE ↗

Affected — Hex / ash_typescript Hex.pm ↗ Repository ↗

0.11.0 < 0.18.0 affected
every other version: unaffected
cpe cpe:2.3:a:ash-project:ash_typescript:*:*:*:*:*:*:*:*
modules · source files · routines
modules 'Elixir.AshTypescript.Rpc.ResultProcessor'
source files lib/ash_typescript/rpc/result_processor.ex
routines 'Elixir.AshTypescript.Rpc.ResultProcessor':normalize_primitive/1 · 'Elixir.AshTypescript.Rpc.ResultProcessor':normalize_value_for_json/1 · 'Elixir.AshTypescript.Rpc.ResultProcessor':normalize_resource_struct/2

Affected — GitHub / ash-project/ash_typescript Repository ↗

9cade76 < aa7f9f1 affected
every other version: unaffected
cpe cpe:2.3:a:ash-project:ash_typescript:*:*:*:*:*:*:*:*
modules · source files · routines
modules 'Elixir.AshTypescript.Rpc.ResultProcessor'
source files lib/ash_typescript/rpc/result_processor.ex
routines 'Elixir.AshTypescript.Rpc.ResultProcessor':normalize_primitive/1 · 'Elixir.AshTypescript.Rpc.ResultProcessor':normalize_value_for_json/1 · 'Elixir.AshTypescript.Rpc.ResultProcessor':normalize_resource_struct/2

Configurations

The application exposes an AshTypescript RPC endpoint over HTTP and relies on Ash field policies to hide attributes on embedded resources that an action returns as a map.

References

Credits

Peter Ullrich Finder Reporter
Torkild Gundersen Kjevik / Ash Project Remediation developer
Jonatan Männchen / EEF Coordinator

CVSS breakdown

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
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