Vulnerability · Published Oct 28, 2026 · Assigned by GitHub_M
CVE-2026-118669OAuthLib: Token grants can use attacker-supplied client_id for authorization after authenticating a different client
High 8.4
In plain English
A high-severity incorrect authorization in oauthlib from oauthlib. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 24% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | python-oauthlib | no fix listed | DEBIAN-CVE-2026-118669 |
| Debian:13 | python-oauthlib | no fix listed | DEBIAN-CVE-2026-118669 |
| Debian:14 | python-oauthlib | no fix listed | DEBIAN-CVE-2026-118669 |
| PyPI | oauthlib | 4.0.0 | GHSA-7984-qgvg-3j9c |
| Ubuntu:22.04:LTS | python-oauthlib | no fix listed | UBUNTU-CVE-2026-118669 |
| Ubuntu:24.04:LTS | python-oauthlib | no fix listed | UBUNTU-CVE-2026-118669 |
| Ubuntu:26.04:LTS | python-oauthlib | no fix listed | UBUNTU-CVE-2026-118669 |
| Ubuntu:26.10 | python-oauthlib | no fix listed | UBUNTU-CVE-2026-118669 |
Affected products (as reported)
Weakness: CWE-863 · 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
References
- https://github.com/oauthlib/oauthlib/security/advisories/GHSA-7984-qgvg-3j9c x_refsource_CONFIRM
- https://github.com/oauthlib/oauthlib/pull/920 x_refsource_MISC
- https://github.com/oauthlib/oauthlib/commit/c951a1d09f99f14e3240973fa83c4f4287d4753d x_refsource_MISC
- https://github.com/oauthlib/oauthlib/releases/tag/v4.0.0 x_refsource_MISC