plone.app.event: Denial of service via iCalendar import

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-55247
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-28 20:18:26 UTC
Updated2026-08-31 19:16:55 UTC
Descriptionplone.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.

Risk And Classification

Primary CVSS: v3.1 9.1 CRITICAL from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H

EPSS: 0.003430000 probability, percentile 0.270360000 (date 2026-09-01)

Problem Types: CWE-400 | CWE-400 CWE-400: Uncontrolled Resource Consumption

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
3.1CNADECLARED9.1CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Plone Plone.app.event affected < 5.2.4 Not specified
CNA Plone Plone.app.event affected >= 6.0.0, < 6.0.1 Not specified

References

ReferenceSourceLinkTags
github.com/plone/plone.app.event/releases/tag/6.0.1 [email protected] github.com
github.com/plone/plone.app.event/releases/tag/5.2.4 [email protected] github.com
github.com/plone/plone.app.event/commit/1e3c83c15a24d1a789cdb012593505bc... [email protected] github.com
github.com/plone/plone.app.event/security/advisories/GHSA-r82h-mqw3-fc56 [email protected] github.com
github.com/plone/plone.app.event/commit/4de5eb3ea9e4f7f1781622e6d64fc086... [email protected] github.com
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