CVE-2026-81853: AshAdmin composite primary key decoding accepts arbitrary fields, enabling a secret-attribute oracle

Severity: low (CVSS 2.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-31 · updated 2026-09-01
Weakness: CWE-639

Description

Authorization Bypass Through User-Controlled Key vulnerability in ash-project ash_admin turns a record-lookup URL into an equality oracle over sensitive attributes. AshAdmin.Helpers.decode_primary_key/2 decodes the composite-primary-key form (Base64 plus ETF) and returns the decoded map verbatim as the lookup filter, without checking that its keys are the resource's primary-key fields. The deserialization guards bound size, block new atoms and funs, and reject nested expressions, but none restricts which fields come back, and :safe still allows any already-interned attribute name. An attacker can therefore encode %{api_token: "guess"} and have it spliced into the lookup filter, brute-forcing a sensitive attribute value (API token, reset token) one equality guess at a time; Map.to_list/1 also accepts structs, yielding a bogus __struct__ key. The fix rejects any decoded key that is not a real primary-key field. This issue affects ash_admin: from 0.1.0 before 1.3.1.

Affected products

ash-project ash_admin: from 0.1.0 before 1.3.1 — fixed in 1.3.1

How to fix

Upgrade to a fixed version: ash-project ash_admin 1.3.1. Check the vendor advisory for mitigations.

References

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