CVE-2026-82758 Auth bypass in ash authentication oauth2 server
An unauthenticated attacker can register OAuth clients by exploiting a fail-open logic flaw in secret resolution, bypassing initial access token requirements.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-82758?
CVE-2026-82758 is a medium-severity authentication bypass vulnerability in ash-project ash_authentication_oauth2_server, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-287
Which versions are affected by CVE-2026-82758?
1 open source package ship an affected version, including ash_authentication_oauth2_server.
| Package | Affected | Fixed in |
|---|---|---|
ash_authentication_oauth2_server Hex | From 0.1.0 | 0.3.1 |
How do I fix CVE-2026-82758?
Upgrade ash_authentication_oauth2_server to 0.3.1 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-82758 being exploited?
There is no known exploitation of CVE-2026-82758 in the wild and no public exploit code.
Sources
Also known as EEF-CVE-2026-82758, GHSA-fxc6-vp68-87pw.