Hi,

The following vulnerability was published for python-oauthlib.

CVE-2026-118669[0]:
| 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.


If you fix the vulnerability please also make sure to include the
CVE (Common Vulnerabilities & Exposures) id in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2026-118669
https://www.cve.org/CVERecord?id=CVE-2026-118669
[1] https://github.com/oauthlib/oauthlib/security/advisories/GHSA-7984-qgvg-3j9c
[2] https://github.com/oauthlib/oauthlib/pull/920
[3] https://github.com/oauthlib/oauthlib/commit/c951a1d09f99f14e3240973fa83c4f4287d4753d

Please adjust the affected versions in the BTS as needed.

Regards,
Salvatore