Cross-site scripting in Products.CMFCore, Products.PluggableAuthService, Plone

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N · score source

EPSS

• CVE-2021-33507: 0.75% estimated exploitation activity in the next 30 days; percentile 55.00 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

18 Jun 2021, 18:44 UTC

Last modified by the source

13 Jul 2026, 16:43 UTC

Source last checked

26 Oct 2026, 13:22 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-35rg-466w-77h3

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-35rg-466w-77h3

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# Patch Next advisory brief: CVE-2021-33507

Advisory: Cross-site scripting in Products.CMFCore, Products.PluggableAuthService, Plone
IDs: CVE-2021-33507, GHSA-35rg-466w-77h3
Record: https://patchnext.com/advisories/cve-2021-33507 (revision 3, source checked 26 Oct 2026, 13:22 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: products-cmfcore 2.5.1; products-pluggableauthservice 2.6.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI products-cmfcore: affected < 2.5.1; fixed in 2.5.1
- PyPI products-pluggableauthservice: affected < 2.6.2; fixed in 2.6.2
- PyPI plone: affected <= 5.2.4

## Suggested inspection (read-only)
- `python -m pip show products-cmfcore`: prints the installed version. Run with the environment that serves production active.
- `python -m pip show products-pluggableauthservice`: prints the installed version. Run with the environment that serves production active.
- `python -m pip show plone`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on products-cmfcore, products-pluggableauthservice, plone.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-35rg-466w-77h3 (OSV record GHSA-35rg-466w-77h3 lists affected ranges: PyPI products-cmfcore >=0 =0 =0 <=5.2.4)
- Verified: https://github.com/advisories/GHSA-35rg-466w-77h3 (GitHub-reviewed advisory GHSA-35rg-466w-77h3 lists affected ranges: PyPI products-cmfcore >=0 =0 =0 <=5.2.4)

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