CVE-2021-32701
Possible bypass of token claim validation when OAuth2 Introspection caching is enabled
In short
When OAuth2 token caching is enabled in ORY Oathkeeper, the system doesn't check if a cached token has the correct permissions (scopes) for a new request, allowing someone to access endpoints they shouldn't be able to reach if their token was recently validated for a different endpoint.
Technical detail
The oauth2_introspection authenticator's cache validation omits scope verification, checking only token expiration. An attacker with a token valid for scope 'foo' can access endpoints requiring scope 'bar' if the token remains cached before expiration, bypassing authorization checks that should fail. This affects ORY Oathkeeper versions prior to v0.38.12-beta.1 when introspection caching is explicitly enabled.
Summary generated and translated by AI from the official description.
ORY Oathkeeper is an Identity & Access Proxy (IAP) and Access Control Decision API that authorizes HTTP requests based on sets of Access Rules. When you make a request to an endpoint that requires the scope `foo` using an access token granted with that `foo` scope, introspection will be valid and that token will be cached. The problem comes when a second requests to an endpoint that requires the scope `bar` is made before the cache has expired. Whether the token is granted or not to the `bar` scope, introspection will be valid. A patch will be released with `v0.38.12-beta.1`. Per default, caching is disabled for the `oauth2_introspection` authenticator. When caching is disabled, this vulnerability does not exist. The cache is checked in [`func (a *AuthenticatorOAuth2Introspection) Authenticate(...)`](https://github.com/ory/oathkeeper/blob/6a31df1c3779425e05db1c2a381166b087cb29a4/pipeline/authn/authenticator_oauth2_introspection.go#L152). From [`tokenFromCache()`](https://github.com/ory/oathkeeper/blob/6a31df1c3779425e05db1c2a381166b087cb29a4/pipeline/authn/authenticator_oauth2_introspection.go#L97) it seems that it only validates the token expiration date, but ignores whether the token has or not the proper scopes. The vulnerability was introduced in PR #424. During review, we failed to require appropriate test coverage by the submitter which is the primary reason that the vulnerability passed the review process.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N