plone.app.event: Denial of service via iCalendar import
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- Low · Low · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-400.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| plone | plone.app.event | before 5.2.4; 6.0.0 to before 6.0.1 | 5.2.4, 6.0.1 | Patch available | CNA |
| — | plone.app.event (PyPI) | before 5.2.4 | 5.2.4 | Patch available | GHSA-r82h-mqw3-fc56 |
| — | plone.app.event (PyPI) | 6.0.0a1 to before 6.0.1 | 6.0.1 | Patch available | GHSA-r82h-mqw3-fc56 |
- plone.app.event Vendorplone Affected before 5.2.4; 6.0.0 to before 6.0.1 Fixed in 5.2.4, 6.0.1 Patch available CNA
- plone.app.event (PyPI) Vendor— Affected before 5.2.4 Fixed in 5.2.4 Patch available GHSA-r82h-mqw3-fc56
- plone.app.event (PyPI) Vendor— Affected 6.0.0a1 to before 6.0.1 Fixed in 6.0.1 Patch available GHSA-r82h-mqw3-fc56
Remediation
- Fix · CNA plone.app.event (plone) Fixed in 5.2.4, 6.0.1
- Fix · GHSA-r82h-mqw3-fc56 plone.app.event (PyPI) Fixed in 5.2.4 Advisory →
- Fix · GHSA-r82h-mqw3-fc56 plone.app.event (PyPI) Fixed in 6.0.1 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-55247
- 2026-10-03 Alias added: GHSA-r82h-mqw3-fc56
References
Other 6
- https://github.com/plone/plone.app.event/security/advisories/GHSA-r82h-mqw3-fc56
- 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
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Sources
- CVE-2026-55247 · CVE Program
- CVE-2026-55247 · NVD
- FIRST EPSS
- GHSA-r82h-mqw3-fc56 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences