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 user's 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:
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An authenticated user with access to a community-distributed event
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The event contains at least one object with a distribution level or sharing group that restricts access beyond the event's own distribution
Impact:
Affected versions: <2.5.48
The fix re-applies the object distribution and sharing-group ACL as a subquery condition on the Attribute.object_id field whenever the flatten option is active. This ensures that attributes belonging to objects the caller is not authorized to see are excluded from the flattened result set. The second commit refines the gate to use only the distribution ACL condition (correlated on Object.id) rather than the entire Object contain, preventing soft-delete state from incorrectly filtering attributes for the event owner.