Executive brief
Decidim is an open-source participatory democracy platform used by organizations and governments to facilitate public debate and decision-making. A security flaw in its API allows unauthorized users to access all commentable resources, potentially exposing private data from restricted participation spaces. This could lead to the disclosure of sensitive internal discussions or community feedback intended to be private.
Technical details
A missing authorization vulnerability (CWE-862) exists in Decidim's GraphQL API. The root-level 'commentable' field fails to perform permission checks, allowing any user—including unauthenticated ones if the /api endpoint is public—to query and retrieve data from any commentable resource on the platform. This bypasses intended access controls for private participation spaces. The vulnerability is exploitable over the network without user interaction. Patches are available in versions 0.30.5 and 0.31.1. Workarounds include restricting /api access to authenticated users or specific IP ranges via middleware or web server configuration.
Affected products
- Decidim decidim-api >= 0.0.1, < 0.30.5; > 0.31.0.rc1, < 0.31.1
- Decidim decidim-comments >= 0.0.1, < 0.30.5; > 0.31.0.rc1, < 0.31.1
Timeline
- 2026-04-13: disclosed: Vulnerability reported to Decidim
- 2026-04-14: advisory: GitHub Advisory published
- 2026-04-21: other: NVD published CVE-2026-40870