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CVE-2026-55247

9.1 · CRITICAL

plone.app.event provides the event content type for Plone.

Published Aug 28, 2026CWE-400EPSS 0.44%

Overview

CVE-2026-55247 is a critical-severity vulnerability. It was published on August 28, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical description

plone.app.event provides the event content type for Plone. Prior to versions 5.2.4 and 6.0.1, the iCalendar import in src/plone/app/event/ical/importer.py accepts insufficiently restricted calendar and event URLs, does not adequately bound downloaded bytes or imported events, and commits work per event. A logged-in editor can make the server request internal network resources or local calendar files, exhaust resources and take the site offline, and store a malicious event URL that executes script in another user's browser. The fix restricts accepted URLs, applies MAXIMUM_ICAL_IMPORT_SIZE_BYTES and MAXIMUM_ICAL_IMPORT_EVENTS limits, uses transaction savepoints, and validates event URLs. This issue is fixed in versions 5.2.4 and 6.0.1.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/plone/plone.app.event/commit/1e3c83c15a24d1a789cdb012593505bc5620e28eGitHubgithub.com/plone/plone.app.event/commit/4de5eb3ea9e4f7f1781622e6d64fc086629d1437GitHubgithub.com/plone/plone.app.event/releases/tag/5.2.4GitHubgithub.com/plone/plone.app.event/releases/tag/6.0.1GitHubgithub.com/plone/plone.app.event/security/advisories/GHSA-r82h-mqw3-fc56

How CyberStrike helps

Frequently asked questions

What is CVE-2026-55247?

CVE-2026-55247 is a critical-severity vulnerability. It was published on August 28, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-55247?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-55247?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-55247?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-55247 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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