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CVE-2026-55247

Denial of service

9.1 CRITICALEPSS 0.44%
  1. Published28 Aug 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredLow
User interactionNone
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

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Frequently asked

Is CVE-2026-55247 being actively exploited?

CVE-2026-55247 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.44%.

How severe is CVE-2026-55247?

CVE-2026-55247 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.44% probability of exploitation.

How do I fix CVE-2026-55247?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-55247 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.