CVE-2026-55248 is a critical-severity (CVSS 9.1) Uncontrolled Resource Consumption vulnerability in plone-app-portlets. O3 Security confirms whether CVE-2026-55248 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
plone.app.portlets vulnerable to denial of service via RSS feed portlet
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55248.
Real-World Exposure
plone-app-portlets🐍plone-app-portlets🐍plone-app-portletsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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.portlets7.0.2 - For Plone 6.1: upgrade to
plone.app.portlets6.0.4 - For Plone 6.0: upgrade to
plone.app.portlets5.0.8
Workarounds
If upgrading is not immediately possible:
- Restrict who can manage portlets: remove the
plone.app.portlets.ManageOwnPortletspermission 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.xmlin 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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | plone-app-portlets | ≥ 7.0.0&&< 7.0.2 | 7.0.2 |
| 🐍PyPI | plone-app-portlets | ≥ 6.0.0&&< 6.0.4 | 6.0.4 |
| 🐍PyPI | plone-app-portlets | all versions | 5.0.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for plone-app-portlets. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update plone-app-portlets to 7.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55248 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-55248 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-55248. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-55248 in your dependencies?
O3 detects CVE-2026-55248 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.