CVSS 3.1
9.1 criticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:HCVE-2026-55247
Critical (9.1). EPSS 0.4% chance of exploitation in the next 30 days. Fixed in plone-app-event 5.2.4, 6.0.1.
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.
Severity
- EPSS
- 0.4% chance of exploitation in the next 30 days; higher than 38% of CVEs (scores of 2026-10-31)
- CWE
- CWE-400
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-r82h-mqw3-fc56 | PyPI | plone-app-event | <5.2.4 | 5.2.4 |
| GHSA-r82h-mqw3-fc56 | PyPI | plone-app-event | >=6.0.0a1 <6.0.1 | 6.0.1 |
| PYSEC-2026-3883 | PyPI | plone-app-event | <5.2.4 >=6.0.0a1 <6.0.1 | 5.2.4, 6.0.1 |
References
- 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