What is CVE-2021-38366?

CVE-2021-38366 is a high-severity vulnerability in Sitecore, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 8.8/10. Published 2021-08-12.

How severe is CVE-2021-38366?

High severity. CVSS v3 base score is 8.8 out of 10.

Arbitrary file upload in Sitecore

CVE-2021-38366

Sitecore through 10.1, when Update Center is enabled, allows remote authenticated users to upload arbitrary files and achieve remote code execution by visiting an uploaded .aspx file at an admin/Packages URL.

Vulnerability class: Unrestricted File Upload

Published 2021-08-12 · last modified 2026-06-17.

CVSS v3 metric

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

EPSS exploit prediction

EPSS: 0.029 (86.5th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 87th percentile — 86.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.029 · newest: 0.029 · change: 0.000

Affected products

Sitecore

Weakness classification (CWE)

CWE-434 — Unrestricted Upload of File with Dangerous Type

References

blog.istern.dk/2021/08/10/sitecore-10-authenticated-file-upload-to-rce/ (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2021-38366?: CVE-2021-38366 is a high-severity vulnerability in Sitecore, classified under Unrestricted Upload of File with Dangerous Type. CVSS score: 8.8/10. Published 2021-08-12.
How severe is CVE-2021-38366?: High severity. CVSS v3 base score is 8.8 out of 10.