What is CVE-2021-33507?

CVE-2021-33507 is a medium-severity vulnerability in Plone, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-05-21.

How severe is CVE-2021-33507?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Plone

CVE-2021-33507

Zope Products.CMFCore before 2.5.1 and Products.PluggableAuthService before 2.6.2, as used in Plone through 5.2.4 and other products, allow Reflected XSS.

Vulnerability class: XSS (Cross-Site Scripting)

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

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.007 (53.1th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 53.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: +0.000

Affected products

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

plone.org/security/hotfix/20210518/reflected-xss-in-various-spots (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-2021-33507?: CVE-2021-33507 is a medium-severity vulnerability in Plone, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-05-21.
How severe is CVE-2021-33507?: Medium severity. CVSS v3 base score is 6.1 out of 10.