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CVE

CVE-2026-40869

Decidim amendments can be accepted or rejected by anyone
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CVE

CVE-2026-40869

Decidim amendments can be accepted or rejected by anyone

Impact

The 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.

The only check done when accepting or rejecting amendments is whether the amendment reactions are enabled for the component:

https://github.com/decidim/decidim/blob/9d6c3d2efe5a83bb02e095824ff5998d96a75eb7/decidim-core/app/permissions/decidim/permissions.rb#L107

The permission checks have been changed at 1b99136 which was introduced in released version 0.19.0. I have not investigated whether prior versions are also affected.

Patches

Not available

Workarounds

Disable amendment reactions for the amendable component (e.g. proposals).

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
7.5
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
C
H
U
0
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
C
H
U
-

Related Resources

No items found.

References

https://github.com/decidim/decidim/security/advisories/GHSA-w5xj-99cg-rccm, https://nvd.nist.gov/vuln/detail/CVE-2026-40869, https://github.com/decidim/decidim/commit/1b99136a1c7aa02616a0b54a6ab88d12907a57a9, https://github.com/decidim/decidim, https://github.com/rubysec/ruby-advisory-db/blob/master/gems/decidim-core/CVE-2026-40869.yml

Severity

7.5

CVSS Score
0
10

Basic Information

Ecosystem
Base CVSS
7.5
EPSS Probability
0.0004%
EPSS Percentile
0.12347%
Introduced Version
0.31.0.rc1,0.19.0
Fix Available
0.31.1,0.30.5

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