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.
CVE-2026-55247
CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence
This critical-severity CVE scores 9.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 73% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
9.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.1Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 9.1
- EG Score
- 9.1(medium)
- EG Risk
- 46(Track)EG Risk 46/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity91% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 27%
- KEV
- Not listed
Published
August 28, 2026
Last Modified
August 28, 2026
Advisory Details (3)
Auto-updated Aug 28, 2026Patch available. Sources: github_commit, github.
github Patch Available
Denial of service via iCalendar import · Advisory · plone/plone.app.event · GitHub
https://github.com/plone/plone.app.event/security/advisories/GHSA-r82h-mqw3-fc56github_commit
commit 4de5eb3ea9e4 (plone/plone.app.event)
Fix landed in plone/plone.app.event commit 4de5eb3ea9e4 — awaiting tagged release
https://github.com/plone/plone.app.event/commit/4de5eb3ea9e4f7f1781622e6d64fc086629d1437github_commit
commit 1e3c83c15a24 (plone/plone.app.event)
Fix landed in plone/plone.app.event commit 1e3c83c15a24 — awaiting tagged release
https://github.com/plone/plone.app.event/commit/1e3c83c15a24d1a789cdb012593505bc5620e28eVendor Advisories for CVE-2026-55247(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 4× in last 7d / 4× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-08-30 01:42 UTCEG score recompute
- 2026-08-30 01:22 UTCEPSS rescore
- 2026-08-28 20:25 UTCEG score recompute
- 2026-08-28 19:10 UTCEG score recompute
Related CVEs(same CWE)
Same CWE
10 shownCWE-400
Frequently asked(5)
What is CVE-2026-55247?
CVE-2026-55247 is a critical vulnerability published on August 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…
When was CVE-2026-55247 disclosed?
CVE-2026-55247 was first published in the National Vulnerability Database on August 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55247 actively exploited?
CVE-2026-55247 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 73.1% of all scored CVEs.
What is the CVSS score of CVE-2026-55247?
CVE-2026-55247 has a CVSS v3 base score of 9.1 (NVD).
How do I remediate CVE-2026-55247?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55247, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-55247
Is Your Infrastructure Affected by CVE-2026-55247?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.