CVE-2023-51447 Decidim vulnerable to cross-site scripting (XSS) in the dynamic file uploads

Medium 6.3 Published 20 Feb 2024 Updated 26 Aug 2024

Attackers can execute arbitrary scripts via malicious file names in dynamic uploads, requiring session control and user interaction.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2023-51447?

CVE-2023-51447 is a medium-severity cross-site scripting vulnerability in decidim, published on 20 Feb 2024. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official 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.

Weakness: CWE-79

Which versions are affected by CVE-2023-51447?

4 open source packages ship an affected version, including decidim and decidim-core. It affects 1 product.

Package	Affected	Fixed in
`decidim` RubyGems	From `0.27.0`	`0.27.5`
`decidim` RubyGems	From `0.27.0`	`0.27.5`
`decidim-core` RubyGems	From `0.27.0`	`0.27.5`
`decidim-core` RubyGems	From `0.27.0`	`0.27.5`

Products include Decidim Decidim.

How do I fix CVE-2023-51447?

Upgrade decidim to 0.27.5 or later.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2023-51447 being exploited?

There is no known exploitation of CVE-2023-51447 in the wild and no public exploit code.

Sources

Also known as GHSA-9w99-78rj-hmxq.