vulnerability / NVI-00009128 / Revision 3
OAuthLib: Token grants can use attacker-supplied client_id for authorization after authenticating a different client
GitHub lists this reviewed advisory for oauthlib. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
8.4 HIGH (4.0)
security-advisories@github.com severity; no combined Null risk score.
0.312%
FIRST EPSS model v2026.06.15; exploitation probability over 30 days, percentile 0.24156. Missing scores are unknown.
As of · FIRST EPSS
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
oauthlib
source listed< 4.0.0
## Summary OAuthlib's token grant handlers can authenticate one client while authorizing the grant type and requested scopes using a different, attacker-supplied `client_id` from the request body. In affected token grant flows, `authenticate_client(request)` sets `request.client` to the authenticated client object, but OAuthlib does not require `request.client_id` to match `request.client.client_id`. If the request body already contains `client_id=...`, OAuthlib keeps that value and passes it to `validate_grant_type()` and `validate_scopes()`. As a result, an authenticated low-privilege confidential client can authenticate as itself, submit another client's `client_id` in the token request body, and cause grant and scope validation to run under that other client identity. ## Affected Surface The affected public surface is the OAuth2 token endpoint handling for: - `client_credentials` - `password` / Resource Owner Password Credentials The issue is relevant to OAuthlib provider deployments where: - the attacker has credentials for one valid lower-privilege confidential client; - another client has broader grants or scopes; - the application validator uses the `client_id` argu
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. FIRST EPSS
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
- NVD lastModified does not establish freshness of every associated CPE record.
05 / Provenance
Sources you can inspect
Each assertion retains its source. Mirrored records may repeat one underlying publisher; additional links are not independent corroboration.
- GHSA-7984-qgvg-3j9c ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
- CVE-2026-118669 ↗
NIST National Vulnerability Database · official catalog
Observed . This product uses data from the NVD API but is not endorsed or certified by the NVD.
- CVE-2026-118669 ↗
FIRST EPSS · official catalog
Observed . FIRST EPSS; probability of exploitation in the next 30 days, not local compromise. Dataset date/model retained; FIRST services terms apply.
Public revision history
Only published revisions appear here. Routine fetches do not create a material-change event.
- Revision 3 ·
Dated EPSS estimate updated; this is not a new disclosure or proof of exploitation.
- Revision 2 ·
Source facts changed; compare the preserved prior revision.
- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.