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Response snapshot Oct 27, 2026, 16:01 UTC

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VulnerabilityCVE-2026-114619

Authlib: OpenID implicit grant checks raw scope instead of allowed scope before issuing ID tokens

| Field | Value | | --- | --- | | Package | `authlib` (PyPI, `pkg:pypi/authlib`) | | Repository | https://github.com/authlib/authlib | | Component | `authlib.oidc.core.grants.implicit.OpenIDImplicitGrant.

Published Updated

At a glance

Exploited
Not known
Severity
4.6 Medium (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: authlib: 1.9.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-q686-2qmg-hqc7 (opens a new tab)

What happened

## Report metadata

| Field | Value | | --- | --- | | Package | `authlib` (PyPI, `pkg:pypi/authlib`) | | Repository | https://github.com/authlib/authlib | | Component | `authlib.oidc.core.grants.implicit.OpenIDImplicitGrant.

validate_authorization_request` | | Vulnerability class | Authorization bypass: a client's scope restriction is bypassed for OpenID Connect ID token issuance | | Verified against | `c529a61af40e3efe05286140e00fbdced07d7987` (v1.8.0). Earlier releases were not checked. | | API surface | Public API (`OpenIDImplicitGrant`, registered with `server.register_grant(...)`) | | Affected in default configuration | Yes.

No non-default option is needed once `OpenIDImplicitGrant` is registered. Client metadata decides exposure: Authlib's standard `ClientMixin` checks response type and scope independently, so a client can be permitted `id_token` responses without being allowed the `openid` scope. |

Continue reading

## Summary

`OpenIDImplicitGrant.validate_authorization_request()` first runs the parent `ImplicitGrant` validation, which filters the requested scope through `client.get_allowed_scope()` and stores the result in `request.scope`. It then decides whether this is an OpenID request by checking the raw, client-supplied `request.payload.scope` instead of that filtered value.

A client that is allowed `profile` but not `openid` can therefore request `scope=openid profile`, pass the check, and receive a signed ID token (with `sub` and profile claims) once the user consents. This happens even when Authlib's built-in, scope-filtering `BearerTokenGenerator` is in use.

The tainted input is the authorization request's `scope` parameter. The OAuth client fully controls it, and the client is the very party the scope restriction is meant to constrain. Any registered client can add `openid` to its request if it is permitted an `id_token` or `id_token token` response type and its allowed scopes exclude `openid` but include a claim-bearing scope such as `profile`.

Sibling paths treat the same client correctly, which suggests the raw-scope check is a bug rather than intended behaviour:

- `ImplicitGrant.validate_authorization_request()` -> filters the requested scope through `client.get_allowed_scope()` into `request.scope` (safe, [`authlib/oauth2/rfc6749/grants/implicit.py` lines 141-147](https://github.com/authlib/authlib/blob/c529a61af40e3efe05286140e00fbdced07d7987/authlib/oauth2/rfc6749/grants/implicit.py#L141-L147)) - `OpenIDImplicitGrant.

validate_authorization_request()` -> **checks the raw `request.payload.scope` (unsafe, [`authlib/oidc/core/grants/implicit.py` line 72](https://github.com/authlib/authlib/blob/c529a61af40e3efe05286140e00fbdced07d7987/authlib/oidc/core/grants/implicit.

py#L72))** - `UserInfoEndpoint` -> rejects the same client's access token with 403 `insufficient_scope` (safe; observed during verification, line not recorded) - OIDC authorization code flow -> issues no `id_token` for the same client (safe; observed during verification, line not recorded)

## Impact

A registered OAuth client that the operator has excluded from the `openid` scope can get an OpenID Connect ID token for any user who logs in and approves its authorization request. During verification the provider returned an RS256-signed ID token carrying `iss`, `aud` (the requesting client), `nonce`, `auth_time`, `at_hash`, `sub` and `name`, while the granted scope was only `profile`.

A consent page built the way the Authlib docs show lists only `profile`, so the user is not shown that an identity token will be issued.

Without this bug, the same request fails with `InvalidScopeError` ("Missing 'openid' scope") because the client's resolved scope does not include `openid`. The new capability is the ID token itself: a signed assertion of the user's identity (`sub`) plus claims from the client's other allowed scopes. Gating that token is exactly what the `openid` scope is for.

The access token stays restricted when the built-in token generator is used: Authlib's `UserInfoEndpoint` rejects it with 403 `insufficient_scope`.

**Scoring note:** we did not compute a CVSS score. An initial triage rated this High. After dynamic verification we assess practical severity as closer to Medium, because:

1. The attacker must be a registered client that is permitted `id_token` response types. 2. The user must log in and consent. 3. The ID token's `aud` is the attacking client.

Two kinds of deployment are not affected:

- Deployments that use only the OIDC authorization code flow. During verification, that flow issued no ID token for the same client. - Deployments where every client permitted an `id_token` or `id_token token` response type is also allowed the `openid` scope.

## Preconditions

1. The authorization server registers `OpenIDImplicitGrant` (or a subclass), e.g. `server.register_grant(MyOpenIDImplicitGrant)`. The vulnerable method runs on every OIDC implicit authorization request. 2. A client's metadata permits an OIDC implicit response type (`id_token` or `id_token token`). Nothing in Authlib ties this to the `openid` scope.

The standard SQLAlchemy `ClientMixin` checks response type and scope independently, and it filters requested scopes against the client's allowed scopes at [`authlib/integrations/sqla_oauth2/client_mixin.py:124-129`](https://github.com/authlib/authlib/blob/c529a61af40e3efe05286140e00fbdced07d7987/authlib/integrations/sqla_oauth2/client_mixin.py#L124-L129). 3.

That client's allowed scopes exclude `openid` but include another claim-bearing scope, such as `profile`. 4. The attacker controls that registered client and sends an authorization request that adds `openid` to otherwise allowed scopes (e.g. `scope=openid profile`), with a `nonce`. 5. A user logs in and approves the request. 6. Branch condition: the raw `request.payload.

scope` contains `openid` while the filtered `request.scope` does not. So `is_openid_scope(self.request.payload.scope)` is true at `implicit.py:72` and no `InvalidScopeError` is ra

Affected package ranges reported by GitHub: authlib: < 1.9.0

Scores and how they were measured

CVSS base severity

4.6

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-q686-2qmg-hqc7 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-q686-2qmg-hqc7, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 27). Authlib: OpenID implicit grant checks raw scope instead of allowed scope before issuing ID tokens (CVE-2026-114619). https://kevwire.com/record/CVE-2026-114619

MLA

"Authlib: OpenID implicit grant checks raw scope instead of allowed scope before issuing ID tokens (CVE-2026-114619)." KEVWire, 27 Oct. 2026, kevwire.com/record/CVE-2026-114619.

Chicago

KEVWire. "Authlib: OpenID implicit grant checks raw scope instead of allowed scope before issuing ID tokens (CVE-2026-114619)." Last modified October 27, 2026. https://kevwire.com/record/CVE-2026-114619.

Evidence summary (plain text)

Authlib: OpenID implicit grant checks raw scope instead of allowed scope before issuing ID tokens (Oct 27, 2026).
| Field | Value |
| --- | --- |
| Package | `authlib` (PyPI, `pkg:pypi/authlib`) |
| Repository | https://github.com/authlib/authlib |
| Component | `authlib.oidc.core.grants.implicit.OpenIDImplicitGrant.validate_authorization_request` |
| Vulnerability class | Authorization bypass: a client's scope restriction is bypassed for OpenID Connect ID token issuance |
| Verified against | `c529a61af40e3efe05286140e00fbdced07d7987` (v1.8.0). Earlier releases were not checked. |
| API surface | Public API (`OpenIDImplicitGrant`, registered with `server.register_grant(...)`) |
| Affected in default configuration | Yes. No non-default option is needed once `OpenIDImplicitGrant` is registered. Client metadata decides exposure: Authlib's standard `ClientMixin` checks response type and scope independently, so a client can be permitted `id_token` responses without being allowed the `openid` scope. |

`OpenIDImplicitGrant.validate_authorization_request()` first runs the parent `ImplicitGrant` validation, which filters the requested scope through `client.get_allowed_scope()` and stores the result in `request.scope`. It then decides whether this is an OpenID request by checking the raw, client-supplied `request.payload.scope` instead of that filtered value. A client that is allowed `profile` but not `openid` can therefore request `scope=openid profile`, pass the check, and receive a signed ID token (with `sub` and profile claims) once the user consents. This happens even when Authlib's built-in, scope-filtering `BearerTokenGenerator` is in use.
CVSS 4.6 (version 3.1; evidence as of Oct 27, 2026; https://github.com/advisories/GHSA-q686-2qmg-hqc7).
Sources:
GitHub-reviewed advisory GHSA-q686-2qmg-hqc7: https://github.com/advisories/GHSA-q686-2qmg-hqc7
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-114619.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 16:00 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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