What is CVE-2021-33509?

CVE-2021-33509 is a critical-severity vulnerability in Plone, classified under Incorrect Permission Assignment for Critical Resource. CVSS score: 9.9/10. Published 2021-05-21.

How severe is CVE-2021-33509?

Critical severity. CVSS v3 base score is 9.9 out of 10.

Vulnerability in Plone

CVE-2021-33509

Plone through 5.2.4 allows remote authenticated managers to perform disk I/O via crafted keyword arguments to the ReStructuredText transform in a Python script.

Published 2021-05-21 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.020 (79.7th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 80th percentile — 79.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.020 · newest: 0.020 · change: +0.000

Affected products

Plone

Weakness classification (CWE)

CWE-732 — Incorrect Permission Assignment for Critical Resource

References

plone.org/security/hotfix/20210518/writing-arbitrary-files-via-docutils-and-pyt… (Vendor Advisory)
www.openwall.com/lists/oss-security/2021/05/22/1 (mailing-list, Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2021-33509?: CVE-2021-33509 is a critical-severity vulnerability in Plone, classified under Incorrect Permission Assignment for Critical Resource. CVSS score: 9.9/10. Published 2021-05-21.
How severe is CVE-2021-33509?: Critical severity. CVSS v3 base score is 9.9 out of 10.