CVE-2026-82758

Received Received - Intake

Improper Authentication in ash_authentication_oauth2_server

Publication date: 2026-09-07

Last updated on: 2026-09-07

Assigner: EEF

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.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-07

Last Modified

2026-09-07

Generated

2026-09-08

AI Q&A

2026-09-08

EPSS Evaluated

N/A

NVD

CVE-2026-82758

Affected Vendors & Products

Vendor	Product	Version / Range
ash-project	ash_authentication_oauth2_server	From 0.1.0 (inc) to 0.3.1 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-287	When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

Attack-Flow Graph

Executive Summary

This vulnerability is an Improper Authentication issue in the ash_authentication_oauth2_server component. It allows an unauthenticated attacker to register OAuth clients even when access should be restricted by an initial access token. The problem occurs because the system incorrectly treats empty or invalid secret values as valid, causing authentication checks to fail open.

Detection Guidance

This vulnerability involves improper authentication in ash_authentication_oauth2_server where unauthenticated attackers can register OAuth clients. To detect it, check if the server version is between 0.1.0 and 0.3.0. Inspect OAuth client registration endpoints for unexpected access. Review server logs for unauthorized client registrations or unusual POST /oauth/register requests.

Impact Analysis

An attacker could exploit this to register unauthorized OAuth clients, potentially gaining access to protected resources or impersonating legitimate users. This could lead to data breaches, unauthorized actions, or further system compromise depending on the OAuth client's permissions.

Compliance Impact

This vulnerability allows unauthorized OAuth client registration due to improper authentication, which could lead to unauthorized access to sensitive data. This may violate compliance requirements under GDPR (data protection) and HIPAA (health information security) by enabling unauthorized data exposure or processing.

Mitigation Strategies

Immediately upgrade ash_authentication_oauth2_server to version 0.3.1 or later to address the improper authentication issue. Review OAuth client registration settings to ensure initial access tokens are properly configured and validated.

Hi! I’m here to help you understand CVE-2026-82758. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70