MISP contains an authorization bypass in the event flattening feature. When a user requests an event with the flatten option enabled, the application removes the Object containment from the query and returns object attributes as top-level event attributes. In doing so, the object-level distribution and sharing-group access control check was not re-applied to those attributes.
As a result, a user who can view a community-distributed event could retrieve attributes belonging to organisation-only objects (distribution level 0) or objects restricted to a specific sharing group, even though the users organisation does not have access to those objects. This constitutes an unauthorized disclosure of sensitive threat intelligence data.
A secondary issue was introduced by the initial remediation: the fix reused the full Object contain conditions (including soft-delete state) as the gate for flattened attributes, causing an event owner requesting deleted attributes to lose all attributes whose parent object was still live. The final fix isolates the distribution ACL condition as the sole gate.
Preconditions:
An authenticated user with access to a community-distributed event
The event contains at least one object with a distribution level or sharing group that restricts access beyond the events own distribution
Impact:
Unauthorized disclosure of attributes belonging to restricted objects
Potential exposure of organisation-specific threat intelligence to other organisations
Affected versions: <2.5.48
Weakness
The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
Potential Mitigations
- 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.
- Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
- For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
- For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
- One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/1.html
- https://cwe.mitre.org/data/definitions/104.html
- https://cwe.mitre.org/data/definitions/127.html
- https://cwe.mitre.org/data/definitions/13.html
- https://cwe.mitre.org/data/definitions/17.html
- https://cwe.mitre.org/data/definitions/39.html
- https://cwe.mitre.org/data/definitions/402.html
- https://cwe.mitre.org/data/definitions/45.html
- https://cwe.mitre.org/data/definitions/5.html
- https://cwe.mitre.org/data/definitions/51.html
- https://cwe.mitre.org/data/definitions/59.html
- https://cwe.mitre.org/data/definitions/60.html
- https://cwe.mitre.org/data/definitions/647.html
- https://cwe.mitre.org/data/definitions/668.html
- https://cwe.mitre.org/data/definitions/76.html
- https://cwe.mitre.org/data/definitions/77.html
- https://cwe.mitre.org/data/definitions/87.html