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 72% 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.

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 v3
9.1
EG Score
9.1(medium)
EG Risk
41(Track)
EG Risk 41/100SSVC: 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 computed
Severity91% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
28%
KEV
Not listed

Published

August 28, 2026

Last Modified

September 9, 2026

Advisory Details (3)

Auto-updated Sep 15, 2026
Patch 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-fc56
github_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/4de5eb3ea9e4f7f1781622e6d64fc086629d1437
github_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/1e3c83c15a24d1a789cdb012593505bc5620e28e

Vendor 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.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
plone-app-event6.0.0, 6.0.0a1, 6.0.0a26.0.1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 13× in last 7d / 42× 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.

  1. 2026-09-18 21:49 UTCEG score recompute
  2. 2026-09-18 19:28 UTCEPSS rescore
  3. 2026-09-17 20:50 UTCEG score recompute
  4. 2026-09-17 19:31 UTCEPSS rescore
  5. 2026-09-16 18:58 UTCEG score recompute
  6. 2026-09-16 14:08 UTCEPSS rescore
  7. 2026-09-16 05:15 UTCEG score recompute
  8. 2026-09-16 05:15 UTCEPSS rescore
  9. 2026-09-15 03:47 UTCEG score recompute
  10. 2026-09-15 03:11 UTCEPSS rescore
  11. 2026-09-13 17:03 UTCEG score recompute
  12. 2026-09-13 16:47 UTCEPSS rescore
  13. 2026-09-12 16:04 UTCEG score recompute
  14. 2026-09-11 15:01 UTCEG score recompute
  15. 2026-09-11 14:53 UTCEPSS rescore
  16. 2026-09-11 10:51 UTCEG score recompute
  17. 2026-09-10 09:43 UTCEG score recompute
  18. 2026-09-10 09:35 UTCEPSS rescore
  19. 2026-09-09 00:26 UTCEG score recompute
  20. 2026-09-08 22:01 UTCEPSS rescore
  21. 2026-09-07 19:11 UTCEG score recompute
  22. 2026-09-07 16:01 UTCEPSS rescore
  23. 2026-09-06 17:29 UTCEG score recompute
  24. 2026-09-06 13:47 UTCEPSS rescore
  25. 2026-09-05 16:25 UTCEG score recompute
Show 17 more
  1. 2026-09-04 15:08 UTCEG score recompute
  2. 2026-09-04 06:46 UTCEG score recompute
  3. 2026-09-04 05:06 UTCEPSS rescore
  4. 2026-09-02 20:23 UTCEG score recompute
  5. 2026-09-02 14:12 UTCEPSS rescore
  6. 2026-09-01 16:37 UTCEG score recompute
  7. 2026-09-01 13:54 UTCEPSS rescore
  8. 2026-09-01 08:09 UTCEG score recompute
  9. 2026-09-01 04:40 UTCEPSS rescore
  10. 2026-08-31 19:31 UTCEG score recompute
  11. 2026-08-31 18:57 UTCEG score recompute
  12. 2026-08-30 22:32 UTCEG score recompute
  13. 2026-08-30 19:17 UTCEPSS rescore
  14. 2026-08-30 01:42 UTCEG score recompute
  15. 2026-08-30 01:22 UTCEPSS rescore
  16. 2026-08-28 20:25 UTCEG score recompute
  17. 2026-08-28 19:10 UTCEG score recompute

Related CVEs(same CWE)

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, with the most recent update on September 9, 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 72.1% 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

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