# 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.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 21 Apr 2026
- **Updated:** 21 Apr 2026
- **Also known as:** GHSA-ghmh-q25g-gxxx

## 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 (Missing Authorization)

## 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.

## Is CVE-2026-40870 being exploited?

There is no known exploitation of CVE-2026-40870 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40870 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-40870 in the wild and no public exploit code.

Affected product: decidim. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40870/ (Markdown: https://insights.sbomify.com/CVE-2026-40870/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40870
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40870
- OSV: https://osv.dev/vulnerability/CVE-2026-40870

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40870/
Summaries are generated and may contain mistakes; the official description above is the record.