CVE-2026-55248: plone.app.portlets: Denial of service via RSS feed portlet
Impact By adding an RSS portlet, and giving this a link to a very large file, a member can cause a denial of service attack, because Plone will use lots of memory. The member could also use different urls to try to get information about the internal network and open port numbers (SSRF). A malicious RSS feed could cause stored XSS, when the url of a feed item is a javascript url.
Patches The problem has been patched in plone.app.portlets.
For Plone 6.2: upgrade to plone.app.portlets 7.0.2 For Plone 6.1: upgrade to plone.app.portlets 6.0.4 For Plone 6.0: upgrade to plone.app.portlets 5.0.8
Workarounds If upgrading is not immediately possible:
- Restrict who can manage portlets: remove the plone.app.portlets.ManageOwnPortlets permission from untrusted roles, and limit Manage portlets to trusted administrators (usually this is already restricted to the Manager and Site Administrator roles). - Where the RSS portlet is not needed, unregister it so it cannot be added. This would need to be done by editing a portlets.xml in your own code, so it is not a quick fix.
References
This is similar to this plone.app.event vulnerability. It was discovered by the Plone Security Team by thinking of similar cases to the plone.app.event problem.
Other sources
plone.app.portlets provides portlets and a Plone-specific user interface for plone.portlets. Prior to 5.0.8, 6.0.4, and 7.0.2, a member who can add an RSS portlet can set its feed URL to a very large response, causing src/plone/app/portlets/portlets/rss.py to download and retain excessive data in memory and deny service. The same RSS URL handling accepts internal hosts, IP addresses, single-word domains, and explicit ports, allowing server-side requests that can probe internal network services and open ports. A malicious feed item can also supply a JavaScript URL that is retained as the item link and can execute script when used by a victim. The affected logic includes rssfeedurlvalidator, normalurlvalidator, RSSFeed.retrieveFeed, RSSFeed.buildItemDict, and the FEEDDATA in-memory cache. This issue is fixed in versions 5.0.8, 6.0.4, and 7.0.2.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/plone.app.portletsto a version that resolves this vulnerability.Fixed in 5.0.8 - Upgrade
Upgrade
pip/plone.app.portletsto a version that resolves this vulnerability.Fixed in 6.0.4 - Upgrade
Upgrade
pip/plone.app.portletsto a version that resolves this vulnerability.Fixed in 7.0.2 - Upgrade
Upgrade
plone.app.portletsto a version that resolves this vulnerability.Fixed in 5.0.8 - Upgrade
Upgrade
plone.app.portletsto a version that resolves this vulnerability.Fixed in 6.0.4 - Upgrade
Upgrade
plone.app.portletsto a version that resolves this vulnerability.Fixed in 7.0.2 - Configuration
Restrict portlet management: remove the `plone.app.portlets.ManageOwnPortlets` permission from untrusted roles, and limit `Manage portlets` to trusted administrators (typically Manager and Site Administrator roles).
Plone portlets security plone.app.portlets.ManageOwnPortlets permission = remove from untrusted roles - Configuration
Where the RSS portlet is not needed, unregister it so it cannot be added.
Plone RSS portlet RSS portlet registration = unregister (if not needed)
Event History
Frequently Asked Questions
Which users can exploit this issue?
A member who can add or manage an RSS portlet can exploit it. The recommended workaround specifically calls for removing the plone.app.portlets.ManageOwnPortlets permission from untrusted roles and limiting portlet management to trusted administrators.
Which releases contain patched versions?
For Plone 6.2, upgrade plone.app.portlets to 7.0.2. For Plone 6.1, upgrade to 6.0.4; for Plone 6.0, upgrade to 5.0.8.
What can be done if an upgrade cannot happen immediately?
Restrict portlet-management permissions to trusted administrators, removing plone.app.portlets.ManageOwnPortlets from untrusted roles. If RSS portlets are not required, unregister the RSS portlet through a portlets.xml file in custom code so it cannot be added.