CVE-2020-26138

Description

FileField with array notation skips validation The FileField class is commonly used for file upload in custom code on a Silverstripe website. This field is designed to be used with a single file upload. PHP allows for submitting multiple values by adding square brackets to the field name. When this is done to a FileField, it will be coerced into allowing multiple files by using this notation. This is not a supported feature, though nothing is done to prevent this. In this scenario, validation such as limiting allowed extensions is not applied, and the FileField->saveInto() behaviour is not triggered. If custom controller logic is used to process the file uploads, it might implicitly rely on validation to be provided by the Form system, which is not the case.

How to fix CVE-2020-26138

To remediate CVE-2020-26138, upgrade the affected package to a fixed version below.

• —upgrade to 4.6.0 or later
• —upgrade to 4.7.4 or later

Is CVE-2020-26138 being exploited?

Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0, < 4.6.0 | >= 4.6.0-rc1, <= 4.6.0-rc1
• >= 3.0.0, < 4.7.4

CVSS scores

References (6)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2020-26138
• WEBforum.silverstripe.org/c/releases
• WEBgithub.com/FriendsOfPHP/security-advisories/blob/master/silverstripe/framework/CVE-2020-26138.yaml
• WEBwww.silverstripe.org/blog/tag/release