Description

Decidim is a participatory democracy framework. Starting in version 0.27.0 and prior to versions 0.27.5 and 0.28.0, the dynamic file upload feature is subject to potential cross-site scripting attacks in case the attacker manages to modify the file names of the records being uploaded to the server. This appears in sections where the user controls the file upload dialogs themselves and has the technical knowledge to change the file names through the dynamic upload endpoint. Therefore I believe it would require the attacker to control the whole session of the particular user but in any case, this needs to be fixed. Successful exploit of this vulnerability would require the user to have successfully uploaded a file blob to the server with a malicious file name and then have the possibility to direct the other user to the edit page of the record where the attachment is attached. The users are able to craft the direct upload requests themselves controlling the file name that gets stored to the database. The attacker is able to change the filename e.g. to `<svg onload=alert('XSS')>` if they know how to craft these requests themselves. And then enter the returned blob ID to the form inputs manually by modifying the edit page source. Versions 0.27.5 and 0.28.0 contain a patch for this issue. As a workaround, disable dynamic uploads for the instance, e.g. from proposals.

Metrics

 

CVSS Version 4.0 CVSS Version 3.x CVSS Version 2.0

NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.

CVSS 4.0 Severity and Vector Strings:

NIST: NVD

N/A

NVD assessment not yet provided.

CVSS 3.x Severity and Vector Strings:

NIST: NVD

Base Score:  N/A

NVD assessment not yet provided.

CNA:  GitHub, Inc.

Base Score:  6.3 MEDIUM

Vector:  CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N

CVSS 2.0 Severity and Vector Strings:

NIST: NVD

Base Score: N/A

NVD assessment not yet provided.

GitHub, Inc. AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N

GitHub, Inc. CWE-79

Decidim is a participatory democracy framework. Starting in version 0.27.0 and prior to versions 0.27.5 and 0.28.0, the dynamic file upload feature is subject to potential cross-site scripting attacks in case the attacker manages to modify the file names of the records being uploaded to the server. This appears in sections where the user controls the file upload dialogs themselves and has the technical knowledge to change the file names through the dynamic upload endpoint. Therefore I believe it

GitHub, Inc. https://github.com/decidim/decidim/commit/aaf72787cf18beeeb6a771c1f7cbb7654b073423 [No types assigned]

GitHub, Inc. https://github.com/decidim/decidim/pull/11612 [No types assigned]

GitHub, Inc. https://github.com/decidim/decidim/releases/tag/v0.27.5 [No types assigned]

GitHub, Inc. https://github.com/decidim/decidim/releases/tag/v0.28.0 [No types assigned]

GitHub, Inc. https://github.com/decidim/decidim/security/advisories/GHSA-9w99-78rj-hmxq [No types assigned]

GitHub, Inc. https://github.com/rails/rails/blob/a967d355c6fee9ad9b8bd115d43bc8b0fc207e7e/activestorage/app/controllers/active_storage/direct_uploads_controller.rb#L14 [No types assigned]