Answer in brief
CVE-2026-55247 records a Critical severity (CVSS 9.1) vulnerability in plone.app.event: Denial of service via iCalendar import. The current sources do not mark it as known exploited. The current feed maps plone/plone.app.event (generic), plone.app.event (pip), plone.app.event (pip). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps plone/plone.app.event (generic), plone.app.event (pip), plone.app.event (pip). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| plone/plone.app.eventgeneric | < 5.2.4 || >= 6.0.0, < 6.0.1 | Not reported |
| plone.app.eventpip | <5.2.4 | 5.2.4 |
| plone.app.eventpip | >=6.0.0a1,<6.0.1 | 6.0.1 |
Published upstream
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 28, 2026
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.
Quoted source text, attributed separately from HOL analysis.