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.

Attack Vector Network

Attack Complexity Low

Privileges Required Low

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact High

Subsequent System Integrity Impact High

Subsequent System Availability Impact None

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
oauthlib oauthlib affected
Version Status Constraints
< 4.0.0 affected —

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Project Subscriptions

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Advisories

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Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/oauthlib/oauthlib/commit/c951a1d09f99f14e3240973fa83c4f4287d4753d cve-icon cve-icon
https://github.com/oauthlib/oauthlib/pull/920 cve-icon cve-icon
https://github.com/oauthlib/oauthlib/releases/tag/v4.0.0 cve-icon cve-icon
https://github.com/oauthlib/oauthlib/security/advisories/GHSA-7984-qgvg-3j9c cve-icon cve-icon
History

Wed, 28 Oct 2026 21:30:00 +0000

Type Values Removed Values Added
Description 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.
Title OAuthLib: Token grants can use attacker-supplied client_id for authorization after authenticating a different client
Weaknesses CWE-863
References
Metrics cvssV4_0

{'score': 8.4, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-28T21:09:58.893Z

Reserved: 2026-10-28T17:25:37.562Z

Link: CVE-2026-118669

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-28T22:17:12.610

Modified: 2026-10-28T22:17:12.610

Link: CVE-2026-118669

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-28T22:30:12Z

Weaknesses