CVE-2026-40869: Decidim amendments can be accepted or rejected by anyone

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-21 · updated 2026-06-17
Weakness: CWE-266

Description

Decidim is a participatory democracy framework. Starting in version 0.19.0 and prior to versions 0.30.5 and 0.31.1, a vulnerability allows any registered and authenticated user to accept or reject any amendments. The impact is on any users who have created proposals where the amendments feature is enabled. This also elevates the user accepting the amendment as the author of the original proposal as people amending proposals are provided coauthorship on the coauthorable resources. Versions 0.30.5 and 0.31.1 fix the issue. As a workaround, disable amendment reactions for the amendable component (e.g. proposals).

Affected products

decidim: from 0.19.0 before 0.30.5; from 0.31.0 before 0.31.1 — fixed in 0.30.5, 0.31.1

How to fix

Upgrade to a fixed version: decidim 0.30.5, 0.31.1. Check the vendor advisory for mitigations.

References

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