CVE-2026-55247
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.34%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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
- 9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
- EPSS
- 0.34% probability · 27th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-400
- Source
- security-advisories@github.com
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.