{"id":"EEF-CVE-2026-82758","summary":"ash_authentication_oauth2_server treats an empty resolved secret as valid, opening the gated Dynamic Client Registration endpoint","details":"## Summary\n\nImproper Authentication vulnerability in ash-project ash_authentication_oauth2_server allows an unauthenticated attacker to register OAuth clients even when Dynamic Client Registration is gated by an initial access token.\n\n`resolve_secret/3` in `AshAuthentication.Oauth2Server` (reached through `__resolve_secret__!`) treated any return other than `{:ok, _}` or `:error` from a configured `{module, function, args}` or 2-arity-function secret provider as a valid secret, wrapping `nil`, `false`, or `\"\"` as `{:ok, value}`. When the `initial_access_token` resolves to such an empty value, `POST /oauth/register` compares the presented bearer token against it and the comparison passes with no token supplied, so registration is open although it was configured closed. The same fail-open affected other resolved secrets such as `signing_secret`.\n\nThis issue affects ash_authentication_oauth2_server: from 0.1.0 before 0.3.1.\n\n## Configurations\n\nReachable only when the server configures an `initial_access_token` (so Dynamic Client Registration is meant to require one) and the configured secret provider returns an empty value (`nil`, `false`, or `\"\"`) or an `{:error, _}` for it, rather than a non-empty binary.","aliases":["CVE-2026-82758","GHSA-fxc6-vp68-87pw"],"modified":"2026-09-08T22:45:02.764947177Z","published":"2026-09-07T22:32:17.027Z","database_specific":{"capec_ids":["CAPEC-115"],"cpe_ids":["cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-287"]},"references":[{"type":"ADVISORY","url":"https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-fxc6-vp68-87pw"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-82758.html"},{"type":"FIX","url":"https://github.com/ash-project/ash_authentication_oauth2_server/commit/30a87101871775d27d79f9ad6f29eafa4779e118"},{"type":"PACKAGE","url":"https://hex.pm/packages/ash_authentication_oauth2_server"}],"affected":[{"package":{"name":"ash_authentication_oauth2_server","ecosystem":"Hex","purl":"pkg:hex/ash_authentication_oauth2_server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.1.0"},{"fixed":"0.3.1"}]}],"versions":["0.1.0","0.1.1","0.1.2","0.1.3","0.2.0","0.2.1","0.2.2","0.3.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-82758.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/ash-project/ash_authentication_oauth2_server","events":[{"introduced":"855b578037c5ded18e8a6e60f42e56bde4905fae"},{"fixed":"30a87101871775d27d79f9ad6f29eafa4779e118"}]}],"versions":["v0.3.0","v0.2.2","v0.2.1","v0.2.0","v0.1.3","v0.1.2","v0.1.1","v0.1.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-82758.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N"}],"credits":[{"name":"Peter Ullrich","type":"FINDER"},{"name":"Peter Ullrich","type":"REPORTER"},{"name":"Zach Daniel / Ash Project","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"COORDINATOR"}]}