CVE-2026-40870 Decidim's comments API allows access to all commentable resources
Attackers can access all commentable resources via the public API without permission checks, exposing potentially private data in Decidim instances.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-40870?
CVE-2026-40870 is a high-severity missing authorization vulnerability in decidim, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Decidim is a participatory democracy framework. Starting in version 0.0.1 and prior to versions 0.30.5 and 0.31.1, the root level `commentable` field in the API allows access to all commentable resources within the platform, without any permission checks. All Decidim instances are impacted that have not secured the `/api` endpoint. The `/api` endpoint is publicly available with the default configuration. Versions 0.30.5 and 0.31.1 fix the issue. As a workaround, limit the scope to only authenticated users by limiting access to the `/api` endpoint. This would require custom code or installing the 3rd party module `Decidim::Apiauth`. With custom code, the `/api` endpoint can be limited to only authenticated users. The same configuration can be also used without the `allow` statements to disable all traffic to the the `/api` endpoint. When considering a workaround and the seriousness of the vulnerability, please consider the nature of the platform. If the platform is primarily serving public data, this vulnerability is not serious by its nature. If the platform is protecting some resources, e.g. inside private participation spaces, the vulnerability may expose some data to the attacker that is not meant public. For those who have enabled the organization setting "Force users to authenticate before access organization", the scope of this vulnerability is limited to the users who are allowed to log in to the Decidim platform. This setting was introduced in version 0.19.0 and it was applied to the `/api` endpoint in version 0.22.0.
Weakness: CWE-862
Which versions are affected by CVE-2026-40870?
How do I fix CVE-2026-40870?
No fix has been published for CVE-2026-40870 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-2026-40870 being exploited?
There is no known exploitation of CVE-2026-40870 in the wild and no public exploit code.
Sources
Also known as GHSA-ghmh-q25g-gxxx.