What is CVE-2020-28736?

CVE-2020-28736 is a high-severity vulnerability in Plone, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 8.8/10. Published 2020-12-30.

How severe is CVE-2020-28736?

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

XXE in Plone

CVE-2020-28736

Plone before 5.2.3 allows XXE attacks via a feature that is protected by an unapplied permission of plone.schemaeditor.ManageSchemata (therefore, only available to the Manager role).

Vulnerability class: XXE (XML External Entity)

Published 2020-12-30 · 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: 0.015 (72.5th percentile), scored 2026-10-03.

Low probability of exploitation in the next 30 days, but still tracked. 73rd percentile — 72.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.014 · newest: 0.015 · change: +0.000

Affected products

Plone

Weakness classification (CWE)

CWE-611 — Improper Restriction of XML External Entity Reference (XXE)

References

www.misakikata.com/codes/plone/python-en.html (Broken Link)
github.com/plone/Products.CMFPlone/issues/3209 (Patch, Third Party Advisory)
dist.plone.org/release/5.2.3/RELEASE-NOTES.txt (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2020-28736?: CVE-2020-28736 is a high-severity vulnerability in Plone, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 8.8/10. Published 2020-12-30.
How severe is CVE-2020-28736?: High severity. CVSS v3 base score is 8.8 out of 10.