CVE-2026-103659 MISP: Object Distribution ACL Bypass via Event Flattening Exposes Organisation-Only Attributes
Authenticated users can bypass access controls to view restricted threat intelligence attributes via event flattening, exposing sensitive organizational data.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-103659?
CVE-2026-103659 is a high-severity missing authorization vulnerability in MISP, published on 1 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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
Which versions are affected by CVE-2026-103659?
How do I fix CVE-2026-103659?
No fix has been published for CVE-2026-103659 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-103659 being exploited?
There is no known exploitation of CVE-2026-103659 in the wild and no public exploit code.
Sources
Also known as GHSA-r4v7-fgm4-552c.