Plone - CraftedSignal Threat Feed

Critical Vulnerabilities in plone.app.portlets RSS Feed Portlet

hello@craftedsignal.io — Fri, 28 Aug 2026 21:13:28 +0000

The Plone Security Team has identified critical security vulnerabilities (CVE-2026-55248) in the plone.app.portlets package. The vulnerabilities stem from the RSS feed portlet implementation. A user with permissions to manage portlets can provide an RSS feed URL pointing to a large file, causing significant memory consumption and leading to a denial of service (DoS). Furthermore, the lack of validation on the RSS URL allows an attacker to conduct server-side request forgery (SSRF) to probe internal network services and discover open ports. Additionally, the RSS feed parser is vulnerable to stored cross-site scripting (XSS) if a feed item contains a URL using the 'javascript:' protocol. These vulnerabilities impact Plone 6.2, 6.1, and 6.0 versions. Organizations should prioritize patching or implementing the recommended access restrictions for the portlet management feature.

Impact

Successful exploitation could result in service instability due to memory exhaustion, unauthorized exposure of internal network topology via SSRF, and potential account takeover or unauthorized actions through stored XSS. These issues affect any organization utilizing the RSS portlet feature within Plone environments.

Recommendation

Upgrade plone.app.portlets immediately to the patched versions: 7.0.2 for Plone 6.2, 6.0.4 for Plone 6.1, and 5.0.8 for Plone 6.0.
Revoke the plone.app.portlets.ManageOwnPortlets permission from untrusted roles to limit the attack surface.
Audit existing portlets to ensure no unauthorized RSS feeds are configured.
If the RSS portlet is not required, unregister it via portlets.xml configuration to mitigate the risk entirely.

Critical Vulnerabilities in plone.app.event

hello@craftedsignal.io — Fri, 28 Aug 2026 21:13:20 +0000

The plone.app.event package, a component used within the Plone content management system, is affected by a series of vulnerabilities (CVE-2026-55247) originating in its iCalendar import functionality. The flaws allow a logged-in editor to conduct a denial-of-service attack, perform Server-Side Request Forgery (SSRF) to read internal network resources or local server files, and execute stored Cross-Site Scripting (XSS) via the event URL field. These vulnerabilities were responsibly reported and patched in versions 5.2.4 and 6.0.1. Due to the nature of the SSRF and DoS vectors, environments where untrusted users possess the 'Editor' role are at high risk of internal reconnaissance and service disruption. There is currently no known workaround for the stored XSS vulnerability.

Impact

Successful exploitation could result in total site unavailability, exfiltration of internal network or local file system data via SSRF, and persistent XSS injection. These vulnerabilities target the administrative and content creation workflows of Plone installations, putting any organization relying on Plone for public or internal content hosting at risk of data breach or operational outages.

Recommendation

Prioritize upgrading plone.app.event to the patched versions: 6.0.1 for Plone 6.2 users, or 5.2.4 for Plone 6.0 and 6.1 users.
Until patching is complete, restrict the "plone.app.event: Import Ical" permission exclusively to the "Manager" role within the Zope Management Interface (manage_access) to limit the attack surface to trusted administrators.
Monitor webserver access logs for anomalous POST requests to calendar import endpoints or requests targeting internal network or local file paths.