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Vulnerability record · CVE-2026-55247 · published 28 August 2026

CVE-2026-55247: Uncontrolled resource consumption vulnerability

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.

9.1 CVSS 3.1 Critical EPSS 0.44% · top 64.2% CWE-400 · Uncontrolled resource consumption Deferred
9.1CVSS 3.1 base score
0.44%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
5References
9 Sep 2026Last modified by NVD

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

References

LinkTags
https://github.com/plone/plone.app.event/commit/1e3c83c15a24d1a789cdb012593505bc5620e28e
https://github.com/plone/plone.app.event/commit/4de5eb3ea9e4f7f1781622e6d64fc086629d1437
https://github.com/plone/plone.app.event/releases/tag/5.2.4
https://github.com/plone/plone.app.event/releases/tag/6.0.1
https://github.com/plone/plone.app.event/security/advisories/GHSA-r82h-mqw3-fc56

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Source: NIST National Vulnerability Database (record CVE-2026-55247), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.