MISP Proposal ACL Bypass: Incomplete Distribution Level Check in Shadow Attribute Access Control

Overview

MISP contains an access control flaw in the proposal (shadow attribute) visibility logic. The authorization check accepted any attribute or object carrying one of the user's sharing groups without verifying the distribution level, and denied the owning organisation access to proposals on its own organisation-only attributes.

• A user belonging to a sharing group could view proposals on attributes or objects with that sharing group, regardless of the attribute's distribution level (levels 1-3 should restrict visibility)

• The owning organisation could not view proposals on its own org-only attributes

Security impact: Unauthorized disclosure of proposed attribute changes to users who should not have access based on distribution level restrictions.

Affected: <2.5.48

Affected

• MISP < 2.5.48

Remediation

The fix enforces the distribution level constraint in the sharing group access check, requiring distribution level 4 (All communities) for the sharing group test to apply. Additionally, the owning organisation is now explicitly granted access to proposals on its own attributes regardless of distribution level, correcting the over-restrictive behavior.