VulnerabilityPublished 27 Oct 2026

CVE-2026-114619: Authlib · OpenID implicit grant checks raw scope instead of allowed scope before issuing ID tokens

Affects authlibSource GCVE Database

Authoritative record:CVE-2026-114619· Medium 4.6

Not known to be exploited · CVSS 4.6 Medium : upgrade to 1.9.0 when convenient.

Data as of 27 Oct 2026, 16:27 UTC

CVSS 3.1 base score

4.6Medium

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 1.9.0

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: Required
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade authlib to 1.9.0.

Affected software

Product	Affected	Fixed in
PyPIauthlib	Affected <1.9.0	Fixed in 1.9.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

## 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. | ## 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

CWE-863Incorrect Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #17OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-863

Technical details

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