How severe is CVE-2026-55248?

CVE-2026-55248 has a CVSS score of 9.1/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-55248?

CVE-2026-55248 affects the following packages: plone-app-portlets (PyPI), plone-app-portlets (PyPI), plone-app-portlets (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-55248?

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.

How do I detect CVE-2026-55248 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for plone-app-portlets, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-55248 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2026-55248 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-55248 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-55248?

CVE-2026-55248 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 36th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-55248?

CVE-2026-55248 is classified as Uncontrolled Resource Consumption (CWE-400). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-55248 published, and has it been updated?

CVE-2026-55248 was published on August 28, 2026 and was last updated on September 11, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

CRITICAL severity

CVE-2026-55248 — plone-app-portlets

CRITICALFix: plone/plone.app.portlets@09da52e

CVE-2026-55248 is a critical-severity (CVSS 9.1) Uncontrolled Resource Consumption vulnerability in plone-app-portlets. A fix is available for plone-app-portlets — see the affected versions and patch details below.

plone.app.portlets: Denial of service via RSS feed portlet

Also known asGHSA-x5g3-w747-2h8qPYSEC-2026-3884

Published

Aug 28, 2026

Updated

Sep 11, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

None indexed

Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs36th percentile — riskier than 36% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-55248 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

3 pkgs affected

🐍plone-app-portlets🐍plone-app-portlets🐍plone-app-portlets

Real-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.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.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`plone-app-portlets`	≥ 7.0.0&&< 7.0.2	7.0.2`pip install --upgrade 'plone-app-portlets==7.0.2'`
🐍PyPI	`plone-app-portlets`	≥ 6.0.0&&< 6.0.4	6.0.4`pip install --upgrade 'plone-app-portlets==6.0.4'`
🐍PyPI	`plone-app-portlets`	all versions	5.0.8`pip install --upgrade 'plone-app-portlets==5.0.8'`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for plone-app-portlets, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### 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.a