Arbitrary file upload in Silverstripe Mimevalidator

CVE-2020-9309

Silverstripe CMS through 4.5 can be susceptible to script execution from malicious upload contents under allowed file extensions (for example HTML code in a TXT file). When these files are stored as protected or draft files, the MIME detection can cause browsers to execute the file contents. Uploads stored as protected or draft files are allowed by default for authorised users only, but can also be enabled through custom logic as well as modules such as silverstripe/userforms. Sites using the previously optional silverstripe/mimevalidator module can configure MIME whitelists rather than extension whitelists, and hence prevent this issue. Sites on the Common Web Platform (CWP) use this module by default, and are not affected.

Vulnerability class: Unrestricted File Upload

Published · last modified .

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.018 (78.1th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 78th percentile — 78.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2020-9309: held from 0.018 to 0.018.

EPSS over last 30 days · oldest: 0.018 · newest: 0.018 · change: 0.000

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2020-9309?
CVE-2020-9309 is a high-severity vulnerability in Silverstripe Mimevalidator, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 8.8/10. Published 2020-07-15.
How severe is CVE-2020-9309?
High severity. CVSS v3 base score is 8.8 out of 10.