In livewire/livewire prior to v2.12.7 and v3.5.2, the file extension of an uploaded file is guessed based on the MIME type. As a result, the actual file extension from the file name is not validated. An attacker can therefore bypass the validation by uploading a file with a valid MIME type (e.g., image/png) and a “.php” file extension.
If the following criteria are met, the attacker can carry out an RCE attack:

• Filename is composed of the original file name using $file->getClientOriginalName()
• Files stored directly on your server in a public storage disk
• Webserver is configured to execute “.php” files

PoC

In the following scenario, an attacker could upload a file called shell.php with an image/png MIME type and execute it on the remote server.

class SomeComponent extends Component
{
    use WithFileUploads;

    #[Validate('image|extensions:png')]
    public $file;

    public function save()
    {
        $this->validate();

        $this->file->storeAs(
            path: 'images',
            name: $this->file->getClientOriginalName(),
            options: ['disk' => 'public'],
        );
    }
}

References

• GHSA-f3cx-396f-7jqp
• https://nvd.nist.gov/vuln/detail/CVE-2024-47823
• livewire/livewire@70503b7
• livewire/livewire#8624
• livewire/livewire@cd168c6