What is CVE-2021-35959?

CVE-2021-35959 is a medium-severity vulnerability in Plone, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-06-30.

How severe is CVE-2021-35959?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Plone

CVE-2021-35959

In Plone 5.0 through 5.2.4, Editors are vulnerable to XSS in the folder contents view, if a Contributor has created a folder with a SCRIPT tag in the description field.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-06-30 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.005 (43.2th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 43.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: +0.000

Affected products

Plone

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

plone.org/security/hotfix/20210518/stored-xss-in-folder-contents (Vendor Advisory)
www.openwall.com/lists/oss-security/2021/06/30/2 (mailing-list, Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2021-35959?: CVE-2021-35959 is a medium-severity vulnerability in Plone, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-06-30.
How severe is CVE-2021-35959?: Medium severity. CVSS v3 base score is 5.4 out of 10.