Improper 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.
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.
This issue affects ash_authentication_oauth2_server: from 0.1.0 before 0.3.1.
{
"cna_assigner": "EEF",
"cwe_ids": [
"CWE-287"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82758.json",
"unresolved_ranges": [
{
"extracted_events": [
{
"introduced": "855b578037c5ded18e8a6e60f42e56bde4905fae"
},
{
"fixed": "30a87101871775d27d79f9ad6f29eafa4779e118"
}
],
"source": "AFFECTED_FIELD"
}
]
}