CVE-2026-118669

CVE-2026-118669 · OAuthLib: Token grants can use attacker-supplied client_id for authorization after authenticating a different client

This page contains facts from public vulnerability sources. Check the original advisory before updating.

OAuthLib is an implementation of the OAuth request-signing logic for Python 3.6+. Prior to 4.0.0, the client_credentials and Resource Owner Password Credentials token grant handlers can authenticate request.client as one confidential client while retaining an attacker-supplied request.client_id for validate_grant_type and validate_scopes. A lower-privilege authenticated client can therefore cause grant and scope authorization to use another client's identity when an application validator relies on the documented client_id argument, potentially issuing tokens with unauthorized grants or scopes. Validators that authorize exclusively from request.client may not be affected. This issue is fixed in version 4.0.0.

CVSS 8.4 · High · EPSS 0.3%

Published

2026-10-28T21:09:58.893Z

Updated

2026-10-28T21:09:58.893Z

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