{"id":"EEF-CVE-2026-65633","summary":"Purpose-limited JWT accepted as full bearer authentication in AshAuthentication","details":"## Summary\n\nImproper Authentication vulnerability in team-alembic AshAuthentication allows purpose-limited JWTs to be replayed as full bearer API credentials when a resource uses stateless bearer-token verification.\n\nThe bearer-token authentication helper `AshAuthentication.Plug.Helpers.retrieve_from_bearer/3` verifies an `Authorization: Bearer` JWT's signature and rejects tokens containing an `act` claim, but performs no check that the token's `purpose` claim equals `user` at the bearer boundary. When the resource is configured with `require_token_presence_for_authentication?: false` (the DSL default), the follow-on `validate_token/3` helper returns `{:ok, nil}` without consulting the token resource, so no downstream check on `purpose` takes place either. As a result, any valid, non-expired JWT the library itself issued for a narrow, single-purpose flow (most notably the `purpose: sign_in` token that WebAuthn always emits during sign-in, and that the Password strategy emits when sign-in tokens are enabled) is accepted directly as a general-purpose bearer credential and resolves to a full `current_user` assignment.\n\nThis bypasses the library's intended token-exchange contract, in which the `sign_in` token is meant to be presented exactly once to a preparation that validates the `purpose` claim and immediately revokes the token. The first use of a still-valid sign-in token presented directly in the `Authorization` header succeeds because the stateless bearer path never scopes it to `purpose == \"user\"`.\n\nAn attacker who obtains a not-yet-exchanged sign-in token for a target subject (for example via log or referrer leakage, an intercepted magic-link delivery channel, or a partially compromised intermediary) can present it as a bearer token and be authenticated as that subject, fully bypassing the intended one-time-use and revocation semantics. Exploitation additionally requires that the host application wire up `retrieve_from_bearer/3` on a reachable route and uses either WebAuthn (sign-in tokens are always issued) or the Password strategy with `sign_in_tokens_enabled?: true`. Resources configured with `require_token_presence_for_authentication?: true` (including applications scaffolded by the Igniter installer since v4.5.0) and the session-based path (`authenticate_resource_from_session/4`) enforce `purpose == \"user\"` against the stored token record and are not affected.\n\nThis issue affects ash_authentication: from 3.10.5 before 4.14.2 and from 5.0.0-rc.0 before 5.0.0-rc.13.\n\n## Configurations\n\nThe bypass is reachable only when a resource uses stateless bearer-token verification, i.e. `require_token_presence_for_authentication?` is `false` (the DSL default). In that mode `validate_token/3` returns `{:ok, nil}` without consulting the token resource, so the JWT's `purpose` claim is the only remaining scoping signal at the bearer boundary and it is never checked. When `require_token_presence_for_authentication?` is `true`, `validate_token/3` looks the token up with `get_token(%{\"jti\" =\u003e jti, \"purpose\" =\u003e \"user\"})`; purpose-limited tokens are stored under their own purpose (`sign_in`, `remember_me`, ...), so that lookup fails and those tokens are rejected. Applications scaffolded by the Igniter installer since v4.5.0 default to `require_token_presence_for_authentication?: true` and are therefore not exposed as generated; applications configured manually or that deliberately opt into stateless JWT verification are.\n\nExploitation additionally requires the host application to wire up `AshAuthentication.Plug.Helpers.retrieve_from_bearer/3` on a route the attacker can reach, and to use a strategy that issues purpose-limited JWTs carrying a resolvable `sub` claim: either the WebAuthn strategy (sign-in tokens are always emitted, no opt-in required) or the Password strategy with `sign_in_tokens_enabled?: true`. The session-based path (`authenticate_resource_from_session/4`) already enforces `purpose == \"user\"` against the token resource and is not affected.","aliases":["CVE-2026-65633","GHSA-6vcj-3h59-rrc3"],"modified":"2026-09-08T04:15:03.798198296Z","published":"2026-08-25T08:03:51.846Z","database_specific":{"cwe_ids":["CWE-287"],"capec_ids":["CAPEC-21"],"cpe_ids":["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"]},"references":[{"type":"ADVISORY","url":"https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-6vcj-3h59-rrc3"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-65633.html"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/8cf8b2d4426172be0900a3505e9491800b951750"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/124eddd1bbeb40289c3fe8831ac10677a19fcf09"},{"type":"PACKAGE","url":"https://hex.pm/packages/ash_authentication"}],"affected":[{"package":{"name":"ash_authentication","ecosystem":"Hex","purl":"pkg:hex/ash_authentication"},"ranges":[{"type":"SEMVER","events":[{"introduced":"3.10.5"},{"fixed":"4.14.2"}]},{"type":"SEMVER","events":[{"introduced":"5.0.0-rc.0"},{"fixed":"5.0.0-rc.13"}]}],"versions":["3.10.5","3.10.6","3.10.7","3.10.8","3.11.0","3.11.1","3.11.10","3.11.11","3.11.12","3.11.13","3.11.14","3.11.15","3.11.16","3.11.2","3.11.3","3.11.4","3.11.5","3.11.6","3.11.7","3.11.8","3.11.9","3.12.0","3.12.1","3.12.2","3.12.3","3.12.4","4.0.0","4.0.0-rc.0","4.0.0-rc.1","4.0.0-rc.2","4.0.0-rc.3","4.0.0-rc.5","4.0.0-rc.6","4.0.1","4.0.2","4.0.3","4.0.4","4.1.0","4.10.0","4.11.0","4.12.0","4.13.0","4.13.1","4.13.2","4.13.3","4.13.4","4.13.5","4.13.6","4.13.7","4.14.0","4.14.1","4.2.0","4.2.1","4.2.2","4.2.3","4.2.4","4.2.5","4.2.6","4.2.7","4.3.0","4.3.1","4.3.10","4.3.11","4.3.12","4.3.2","4.3.3","4.3.4","4.3.5","4.3.6","4.3.7","4.3.8","4.3.9","4.4.0","4.4.1","4.4.2","4.4.3","4.4.4","4.4.5","4.4.6","4.4.7","4.4.8","4.4.9","4.5.0","4.5.1","4.5.2","4.5.3","4.5.4","4.5.5","4.5.6","4.6.0","4.6.1","4.6.2","4.6.3","4.6.4","4.7.0","4.7.1","4.7.2","4.7.3","4.7.4","4.7.5","4.7.6","4.8.0","4.8.1","4.8.2","4.8.3","4.8.5","4.8.6","4.8.7","4.9.0","4.9.1","4.9.2","4.9.3","4.9.4","4.9.5","4.9.6","4.9.7","4.9.8","4.9.9","5.0.0-rc.0","5.0.0-rc.1","5.0.0-rc.10","5.0.0-rc.11","5.0.0-rc.12","5.0.0-rc.2","5.0.0-rc.3","5.0.0-rc.4","5.0.0-rc.5","5.0.0-rc.6","5.0.0-rc.7","5.0.0-rc.8","5.0.0-rc.9"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-65633.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/team-alembic/ash_authentication","events":[{"introduced":"eca8cadea0f1595ed2c10a0c177b1da9aa9e5269"},{"fixed":"8cf8b2d4426172be0900a3505e9491800b951750"},{"fixed":"124eddd1bbeb40289c3fe8831ac10677a19fcf09"}]}],"versions":["v4.14.1","v5.0.0-rc.12","v5.0.0-rc.11","v5.0.0-rc.10","v4.14.0","v4.13.7","5.0.0-rc.9","5.0.0-rc.8","v5.0.0-rc.7","v5.0.0-rc.6","v5.0.0-rc.5","v5.0.0-rc.4","v5.0.0-rc.3","v5.0.0-rc.2","v5.0.0-rc.1","v5.0.0-rc.0","v4.13.6","v4.13.5","v4.13.4","v4.13.3","v4.13.2","v4.13.1","v4.13.0","v4.12.0","v4.11.0","v4.10.0","v4.9.9","v4.9.8","v4.9.7","v4.9.6","v4.9.5","v4.9.4","v4.9.3","v4.9.2","v4.9.1","v4.9.0","v4.8.7","v4.8.5","v4.8.4","v4.8.3","v4.8.2","v4.8.1","v4.8.0","v4.7.7","v4.7.6","v4.7.5","v4.7.4","v4.7.3","v4.7.2","v4.7.1","v4.7.0","v4.6.4","v4.6.3","v4.6.2","v4.6.1","v4.6.0","v4.5.6","v4.5.5","v4.5.4","v4.5.3","v4.5.2","v4.5.1","v4.4.9","v4.4.8","v4.4.7","v4.4.6","v4.4.5","v4.4.4","v4.4.3","v4.4.2","v4.4.1","v4.4.0","v4.3.12","v4.3.10","v4.3.9","v4.3.7","v4.3.6","v4.3.4","v4.3.3","v4.3.2","v4.3.1","v4.3.0","v4.2.7","v4.2.5","v4.2.3","v4.2.2","v4.2.1","v4.2.0","v4.1.0","v4.0.4","v4.0.3","v4.0.2","v4.0.1","v4.0.0","v4.0.0-rc.7","v4.0.0-rc.6","v4.0.0-rc.5","v4.0.0-rc.4","v4.0.0-rc.3","v4.0.0-rc.2","v4.0.0-rc.1","v4.0.0-rc.0","v3.12.4","v3.12.3","v3.12.2","v3.12.1","v3.12.0","v3.11.16","v3.11.15","v3.11.14","v3.11.13","v3.11.12","v3.11.10","v3.11.9","v3.11.8","v3.11.7","v3.11.6","v3.11.5","v3.11.4","v3.11.3","v3.11.2","v3.11.1","v3.11.0","v3.10.8","v3.10.7","v3.10.6","v3.10.5"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-65633.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"}],"credits":[{"name":"EQSTLab","type":"FINDER"},{"name":"James Harton","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"COORDINATOR"}]}