by Kastro
Paper/Archive/CVE-2026-55247

CVE-2026-55247

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

EPSS 0.4%CVSS 9.1
critical.is priorityof 100
35
CVSS 9.1 (CNA)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 38.3.383 × 207.7No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
plone.app.event< 5.2.4–CNA
plone.app.event>= 6.0.0, < 6.0.1–CNA

Scores by source

GitHub_M (CNA)9.1CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: partial

References

refgithub.com/plone/plone.app.event/security/advisories/GHSA-r82h-mqw3-fc56refgithub.com/plone/plone.app.event/commit/1e3c83c15a24d1a789cdb012593505bc5620e28erefgithub.com/plone/plone.app.event/commit/4de5eb3ea9e4f7f1781622e6d64fc086629d1437refgithub.com/plone/plone.app.event/releases/tag/5.2.4refgithub.com/plone/plone.app.event/releases/tag/6.0.1