EUVD-2026-72540Severity by source
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network-reachable endpoint but AC:H because exploitation requires a specific misconfigured secret provider returning nil/false/empty; no confidentiality or availability impact, only low integrity from unauthorized client registration.
Primary rating from Vendor (EEF).
CVSS VectorVendor: EEF
Lifecycle Timeline
2DescriptionCVE.org
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.
AnalysisAI
Dynamic Client Registration (DCR) bypass in ash_authentication_oauth2_server versions 0.1.0 through 0.3.0 allows unauthenticated network attackers to register OAuth clients on servers that were configured to require an initial access token. The root cause is a fail-open pattern in resolve_secret/3: when a configured secret provider returned nil, false, or an empty string instead of a structured :error tuple, the function wrapped the value as {:ok, value} and passed it to the bearer-token comparison, causing that comparison to succeed against any request. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires three specific conditions to align. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 vector supplied by the vendor (AV:N/AC:L/AT:P/PR:N/UI:N) with an overall score of 6.3 reflects the conditional nature of the vulnerability: AT:P (Attack Requirements: Present) captures the prerequisite that the operator's secret provider must return nil, false, or an empty string rather than a proper :error - a meaningful condition since compliant providers should always return one of the two expected tuples. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade ash_authentication_oauth2_server to version 0.3.1 or later, which introduces the normalize_resolved_secret/1 helper ensuring any non-binary or empty-binary secret resolution fails closed with :error rather than wrapping the bad value as {:ok, value}. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Unauthenticated resource exhaustion in ash_authentication_oauth2_server 0.3.0 enables any remote attacker to grow databa
OAuth2 state-changing protocol endpoints in ash_authentication_oauth2_server (versions 0.1.0 through 0.3.0) are silently
WWW-Authenticate header parameter injection in ash_authentication_oauth2_server (versions 0.1.3 through 0.3.0) allows un
SSRF in ash_authentication_oauth2_server 0.3.0 allows an attacker who controls both an OAuth2 client's metadata URL and
Multi-tenant OAuth2 metadata cross-tenant leakage in ash_authentication_oauth2_server (versions 0.1.3 through before 0.3
Same weakness CWE-287 – Improper Authentication
View allSame technique Authentication Bypass
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External POC / Exploit Code
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