CVE-2026-82758

Summary

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.

Affected Software

Weaknesses

• CWE-287: CWE-287 Improper Authentication

References

• https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-fxc6-vp68-87pw
• https://cna.erlef.org/cves/CVE-2026-82758.html
• https://osv.dev/vulnerability/EEF-CVE-2026-82758
• https://github.com/ash-project/ash_authentication_oauth2_server/commit/30a87101871775d27d79f9ad6f29eafa4779e118

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