CVE-2026-118669
OAuthLib: Token grants can use attacker-supplied client_id for authorization after authenticating a different client
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
- oauthlib
- CVSS v4.0 GITHUB
- 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS v4.0 GitHub
- 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 - EPSS
- 0.31% chance of exploitation in the next 30 days, 24th percentile
- Published
- 2026-10-28
Proof-of-concept exploits (1)
CVE references
- oauthlib/oauthlib/commit/c951a1d09f99f14e3240973fa83c4f4287d4753dREFERENCE
- oauthlib/oauthlib/pull/920REFERENCE
- oauthlib/oauthlib/releases/tag/v4.0.0REFERENCE
- oauthlib/oauthlib/security/advisories/GHSA-7984-qgvg-3j9cREFERENCE