EEF-CVE-2026-82758 CVE-2026-82758 GHSA-fxc6-vp68-87pw
ash_authentication_oauth2_server treats an empty resolved secret as valid, opening the gated Dynamic Client Registration endpoint
- Severity
- 0.0 / 10
- Unknown · CVSS 4.0
- Exploit chance (EPSS)
- 0.69%
- Chance of exploitation in the next 30 days. Higher than 52.66% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-287 Improper Authentication
- Fix
0.3.1- Upgrade ash_authentication_oauth2_server to this version or later
Description
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.
Configurations
Reachable 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.
Affected versions
Hex
| Package | Vulnerable | Fixed in |
|---|---|---|
| ash_authentication_oauth2_server | >= 0.1.0, < 0.3.1 |
0.3.1 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
ash_authentication_oauth2_server Hex → 0.3.1
- mix
{:ash_authentication_oauth2_server, "~> 0.3.1"} # then: mix deps.update ash_authentication_oauth2_server
Severity breakdown
CVSS 4.0 0.0
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
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- Present
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- Low
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
Weakness
CWE-287: Improper Authentication
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
How to prevent it
- Architecture and Design: Use an authentication framework or library such as the OWASP ESAPI Authentication feature.
References
Advisories
Fixes and patches
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| EEF-CVE-2026-82757 ash_authentication_oauth2_server CIMD fetcher classifies IPv4-in-IPv6 and site-local addresses as public, allowing SSRF | Not rated yet | Also affects ash_authentication_oauth2_server |
| EEF-CVE-2026-82756 ash_authentication_oauth2_server interpolates a tenant-derived value into the WWW-Authenticate challenge without escaping, allowing header parameter injection | Not rated yet | Also affects ash_authentication_oauth2_server |
| EEF-CVE-2026-82755 ash_authentication_oauth2_server serves tenant-specific OAuth metadata as publicly cacheable without Vary, enabling cross-tenant confusion | Not rated yet | Also affects ash_authentication_oauth2_server |
| EEF-CVE-2026-82754 ash_authentication_oauth2_server aliases every protocol endpoint under /.well-known, bypassing path-scoped controls | Not rated yet | Also affects ash_authentication_oauth2_server |
| EEF-CVE-2026-82753 Unauthenticated authorize requests create unbounded, never-expiring CIMD client rows and cache entries in ash_authentication_oauth2_server | Not rated yet | Also affects ash_authentication_oauth2_server |
| GHSA-f9x3-7vq9-cph6 Laravel TokenGuard authentication bypass through non-string API credentials | Critical | Same weakness, CWE-287 |
| GHSA-r4xp-prcw-77qf better-auth: OAuth Proxy lets an attacker sign in as another user | Critical | Same weakness, CWE-287 |
| GHSA-965c-763c-88jm better-auth: OAuth state can be used as a Magic Link to sign in as another user | Critical | Same weakness, CWE-287 |
Credits: Jonatan Männchen / EEF, Peter Ullrich, Zach Daniel / Ash Project
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