CVE-2026-55247Critical· 9.1▾ Midnightplone.app.event vulnerable to denial of service via iCalendar import
▾ Midnight zone — Critical, or high with PoC / in-the-wild
impact 50.1 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Aug 29.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
0.3%
Last analysed / modified upstream
By abusing the iCalendar import functionality, a logged-in editor could take the whole site offline, make the server reach into the internal network and read calendar files off disk (SSRF), and store XSS.
The problem has been patched in plone.app.event.
plone.app.event 6.0.1plone.app.event 5.2.4plone.app.event 5.2.4In the site root, go to the Security tab of the Zope Management Interface (manage_access), look for the "plone.app.event: Import Ical" permission, and grant this only to the Manager role. Then only users with the Manager role can use the ical import form.
There is no workaround for the stored XSS in the URL field of events.
The vulnerabilities were discovered by Timothy Dudley and responsibly reported to the Plone Security Team. Thank you!
plone-app-event < 5.2.4plone-app-event >= 6.0.0a1, < 6.0.1Upgrade to a patched release:
plone-app-event 5.2.4plone-app-event 6.0.1Connected by shared product, vendor, weakness, or advisory.
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