SSRF attacks via tracebacks in Plone

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2020-28735: 1.45% estimated exploitation activity in the next 30 days; percentile 73.46 (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.

Plone before 5.2.3 allows SSRF attacks via the tracebacks feature (only available to the Manager role).

Published by the source

7 Apr 2021, 21:13 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-x7wf-5mjc-6x76

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-x7wf-5mjc-6x76

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2020-28735

Advisory: SSRF attacks via tracebacks in Plone
IDs: CVE-2020-28735, GHSA-x7wf-5mjc-6x76
Record: https://patchnext.com/advisories/cve-2020-28735 (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: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: plone-app-theming 4.1.6; plone-app-event 3.2.10; plone-app-dexterity 2.6.8; plone-supermodel 1.6.3; plone 5.2.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI plone-app-theming: affected < 4.1.6; fixed in 4.1.6
- PyPI plone-app-event: affected < 3.2.10; fixed in 3.2.10
- PyPI plone-app-dexterity: affected < 2.6.8; fixed in 2.6.8
- PyPI plone-supermodel: affected < 1.6.3; fixed in 1.6.3
- PyPI plone: affected < 5.2.3; fixed in 5.2.3

## Suggested inspection (read-only)
- `python -m pip show plone-app-theming`: prints the installed version. Run with the environment that serves production active.
- `python -m pip show plone-app-event`: prints the installed version. Run with the environment that serves production active.
- `python -m pip show plone-app-dexterity`: prints the installed version. Run with the environment that serves production active.
- `python -m pip show plone-supermodel`: 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
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on plone-app-theming, plone-app-event, plone-app-dexterity, plone-supermodel, 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-x7wf-5mjc-6x76 (OSV record GHSA-x7wf-5mjc-6x76 lists affected ranges: PyPI plone >=0 =0 =0 =0 =0 <1.6.3 (fixed))
- Verified: https://github.com/advisories/GHSA-x7wf-5mjc-6x76 (GitHub-reviewed advisory GHSA-x7wf-5mjc-6x76 lists affected ranges: PyPI plone >=0 =0 =0 =0 =0 <1.6.3)

Commands are suggestions: review each one before running it.