CVE-2026-103659: MISP: Object Distribution ACL Bypass via Event Flattening Exposes Organisation-Only Attributes
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:
- 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 event's 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
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
MISPto a version that resolves this vulnerability.Fixed in 2.5.48
Event History
Frequently Asked Questions
Which users could access data they were not authorized to see?
Authenticated users who could view a community-distributed event were affected if that event contained objects restricted to the owning organisation or to a sharing group the user's organisation could not access. Those users could receive attributes from the restricted objects when requesting the event in flattened form.
What request condition was required to trigger the disclosure?
The user needed to request an accessible event with the flatten option enabled. The event also needed to contain attributes within an organisation-only object or an object limited to a sharing group unavailable to that user's organisation.
Is there any implementation concern when applying the remediation?
Yes. An initial remediation incorrectly used the full object containment conditions, including soft-delete state, and could hide attributes from an event owner when the parent object remained live. The final remediation limits the flattened-attribute gate to the distribution ACL condition.