# CVE-2026-40869: Decidim decidim-core incorrect privilege assignment in amendments

Source: https://junglewise.ai/threats/cve-2026-40869-decidim-decidim-core-incorrect-privilege-assignment-in-amendments  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-21. Updated: 2026-05-29  
License: CC BY 4.0 with a link back

CVE-2026-40869 · Severity: high · CVSS 7.5 · Published 2026-04-21

Decidim, a framework for participatory democracy, contains a flaw where any registered user can accept or reject proposed changes (amendments) to proposals. This allows unauthorized individuals to manipulate community proposals and potentially gain co-authorship rights over content they did not create. This could lead to misinformation, unauthorized modification of community initiatives, and damage to the integrity of the democratic process.

Technologies: [Decidim](https://junglewise.ai/threats/technologies/decidim), [decidim-core (RubyGems)](https://junglewise.ai/threats/technologies/decidim-core). Vendors: [Decidim](https://junglewise.ai/threats/vendors/decidim), [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2026-40869 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-40869 being exploited in the wild.

**How severe is CVE-2026-40869?** High severity, with a CVSS score of 7.5, published 21 April 2026.

**Which products and versions are affected?** decidim-core (RubyGems) ECOSYSTEM:introduced=0.31.0.rc1,fixed=0.31.1.

**Is there a fix for CVE-2026-40869?** Yes. decidim-core (RubyGems): upgrade to 0.31.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-40869 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-40869?** Check whether you run Decidim or decidim-core (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- decidim-core (RubyGems): upgrade to 0.31.1 or later

  ```sh
  bundle update decidim-core
  ```


## Technical details

An incorrect privilege assignment (CWE-266) in Decidim's permission logic allows any authenticated user to perform 'accept' or 'reject' actions on amendments. The root cause is located in `decidim-core/app/permissions/decidim/permissions.rb`, where the system only checks if amendment reactions are enabled for a component rather than verifying if the user has the authority to manage the specific amendment. Exploitation allows an attacker to modify the status of any amendment and gain co-authorship status on the associated resource. The issue was introduced in version 0.19.0 and is fixed in versions 0.30.5 and 0.31.1.

## Affected products

- Decidim decidim-core >= 0.19.0, < 0.30.5; >= 0.31.0.rc1, < 0.31.1

## Identifiers

- CVE-2026-40869
- GHSA-w5xj-99cg-rccm

## Timeline

- 2019-06-17: other: Vulnerability introduced in commit 1b99136 (v0.19.0)
- 2026-04-13: disclosed
- 2026-04-14: advisory
- 2026-04-21: other: NVD published CVE-2026-40869

## References

- [https://github.com/decidim/decidim/security/advisories/GHSA-w5xj-99cg-rccm](https://github.com/decidim/decidim/security/advisories/GHSA-w5xj-99cg-rccm)
- [https://github.com/decidim/decidim/commit/1b99136a1c7aa02616a0b54a6ab88d12907a57a9](https://github.com/decidim/decidim/commit/1b99136a1c7aa02616a0b54a6ab88d12907a57a9)
- [https://github.com/rubysec/ruby-advisory-db/blob/master/gems/decidim-core/CVE-2026-40869.yml](https://github.com/rubysec/ruby-advisory-db/blob/master/gems/decidim-core/CVE-2026-40869.yml)
- [https://api.github.com/repos/decidim/decidim/security-advisories/GHSA-w5xj-99cg-rccm](https://api.github.com/repos/decidim/decidim/security-advisories/GHSA-w5xj-99cg-rccm)

## Related threats

- [Decidim decidim-core SSRF in push notification subscriptions](https://junglewise.ai/threats/cve-2026-45573-decidim-decidim-core-ssrf-in-push-notification-subscriptions)
- [Decidim stored XSS in HTML content blocks](https://junglewise.ai/threats/cve-2026-45572-decidim-stored-xss-in-html-content-blocks)
- [Decidim JWT authentication replay across organizations](https://junglewise.ai/threats/cve-2026-45414-decidim-jwt-authentication-replay-across-organizations)
- [Decidim improper access control in Private Data Exports](https://junglewise.ai/threats/cve-2026-45377-decidim-improper-access-control-in-private-data-exports)
- [Decidim SQL injection in administrative user search](https://junglewise.ai/threats/cve-2026-45376-decidim-sql-injection-in-administrative-user-search)