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

Status: published. Published: 2026-10-28. Updated: 2026-11-03.

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.

## Remediation

- fix: oauthlib (PyPI): OSV reports a fixed version 4.0.0. Check the advisory for supported release branches. (source: OSV GHSA-7984-qgvg-3j9c) — https://github.com/advisories/GHSA-7984-qgvg-3j9c

## Affected products and versions

- oauthlib / oauthlib: < 4.0.0 (affected). Source: CNA: GitHub_M
-  / oauthlib (oauthlib): 0.0.1 (affected, PyPI); 0.0.2 (affected, PyPI); 0.1.0 (affected, PyPI); 0.1.1 (affected, PyPI); 0.1.2 (affected, PyPI); 0.1.3 (affected, PyPI); 0.3.0 (affected, PyPI); 0.3.2 (affected, PyPI); 0.3.3 (affected, PyPI); 0.3.4 (affected, PyPI); 0.3.5 (affected, PyPI); 0.3.6 (affected, PyPI); 0.3.7 (affected, PyPI); 0.3.8 (affected, PyPI); 0.4.0 (affected, PyPI); 0.4.1 (affected, PyPI); 0.4.2 (affected, PyPI); 0.5.0 (affected, PyPI); 0.5.1 (affected, PyPI); 0.6.0 (affected, PyPI); 0.6.1 (affected, PyPI); 0.6.2 (affected, PyPI); 0.6.3 (affected, PyPI); 0.7.0 (affected, PyPI); 0.7.1 (affected, PyPI); 0.7.2 (affected, PyPI); 1.0.0 (affected, PyPI); 1.0.1 (affected, PyPI); 1.0.2 (affected, PyPI); 1.0.3 (affected, PyPI); 1.1.0 (affected, PyPI); 1.1.1 (affected, PyPI); 1.1.2 (affected, PyPI); 2.0.0 (affected, PyPI); 2.0.1 (affected, PyPI); 2.0.2 (affected, PyPI); 2.0.3 (affected, PyPI); 2.0.4 (affected, PyPI); 2.0.5 (affected, PyPI); 2.0.6 (affected, PyPI); 2.0.7 (affected, PyPI); 2.1.0 (affected, PyPI); 3.0.0 (affected, PyPI); 3.0.1 (affected, PyPI); 3.0.2 (affected, PyPI); 3.1.0 (affected, PyPI); 3.1.1 (affected, PyPI); 3.2.0 (affected, PyPI); 3.2.1 (affected, PyPI); 3.2.2 (affected, PyPI); 3.3.0 (affected, PyPI); 3.3.1 (affected, PyPI); Ecosystem version events: introduced 0; fixed 4.0.0. Source: OSV GHSA-7984-qgvg-3j9c

## Severity and prioritization

- CVSS 4.0: 8.4 (high); 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; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: 0.31% as of 2026-11-02; percentile 24.14%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-863

## Exploit evidence

- exploit: https://github.com/oauthlib/oauthlib/security/advisories/GHSA-7984-qgvg-3j9c (ADP: CISA-ADP)

## References

- https://github.com/oauthlib/oauthlib/security/advisories/GHSA-7984-qgvg-3j9c (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/oauthlib/oauthlib/pull/920 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/oauthlib/oauthlib/commit/c951a1d09f99f14e3240973fa83c4f4287d4753d (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/oauthlib/oauthlib/releases/tag/v4.0.0 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/oauthlib/oauthlib/security/advisories/GHSA-7984-qgvg-3j9c (ADP: CISA-ADP; exploit)

- https://github.com/advisories/GHSA-7984-qgvg-3j9c (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-7984-qgvg-3j9c (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-118669; retrieved 2026-11-03; source updated 2026-11-03

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-7984-qgvg-3j9c; retrieved 2026-11-03; source updated 2026-10-30

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-118669; retrieved 2026-11-03; source updated Not reported

Revision: dbac7c0f7cae4a2d380f44578fe117d9b573fcd4d2f9e3c94b38459bf7c56111

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