CVE-2026-55247

CRITICALPre-NVD 9.19.1
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This critical-severity CVE scores 9.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4% (36th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
9.1EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 9.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
9.1CRITICALmedium confidence
EG Risk
41
EG Risk 41/100

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 (value × EchelonGraph’s weight)
Severity91% × 45%
The EG Score, 9.1 of 10.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.4%
EPSS %ILE
36th
KEV
Not listed

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 28, 2026

Last Modified

September 9, 2026

Advisory Details (3)

Auto-updated Sep 15, 2026
Patch available. Sources: github_commit, github.
GitHub advisoryMentions a patch (unverified)

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 rangeFix by version rangeDependents
plone-app-event1.0 ... 6.0.0a2 (128 versions)
  • every version up to 5.2.4: fixed in 5.2.4
  • 6.0.0a1 up to 6.0.1: fixed in 6.0.1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 16× in last 7d / 59× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

  1. 2026-10-14 09:33 UTCEG score recompute
  2. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  3. 2026-10-13 07:12 UTCEG score recompute
  4. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  5. 2026-10-12 15:55 UTCEG score recompute
  6. 2026-10-11 19:39 UTCEG score recompute
  7. 2026-10-11 16:54 UTCEG score recompute
  8. 2026-10-11 14:17 UTCEG score recompute
  9. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  10. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  11. 2026-10-10 00:49 UTCEG score recompute
  12. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  13. 2026-10-09 02:37 UTCEG score recompute
  14. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  15. 2026-10-08 00:50 UTCEG score recompute
  16. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  17. 2026-10-06 15:55 UTCEG score recompute
  18. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  19. 2026-10-05 20:59 UTCEG score recompute
  20. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  21. 2026-10-04 23:45 UTCEG score recompute
  22. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  23. 2026-10-03 17:47 UTCEG score recompute
  24. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  25. 2026-10-02 18:56 UTCEG score recompute
Show 66 more
  1. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.4% · 36th percentile
  2. 2026-10-02 00:36 UTCEG score recompute
  3. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  4. 2026-09-30 19:48 UTCEG score recompute
  5. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  6. 2026-09-30 03:49 UTCEG score recompute
  7. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  8. 2026-09-29 01:17 UTCEG score recompute
  9. 2026-09-28 15:47 UTCEG score recompute
  10. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  11. 2026-09-27 14:23 UTCEG score recompute
  12. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  13. 2026-09-26 20:24 UTCEG score recompute
  14. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  15. 2026-09-26 08:03 UTCEG score recompute
  16. 2026-09-24 18:42 UTCEG score recompute
  17. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  18. 2026-09-23 20:31 UTCEG score recompute
  19. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  20. 2026-09-22 15:05 UTCEG score recompute
  21. 2026-09-21 22:25 UTCEG score recompute
  22. 2026-09-20 21:00 UTCEG score recompute
  23. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  24. 2026-09-19 18:45 UTCEG score recompute
  25. 2026-09-18 21:49 UTCEG score recompute
  26. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  27. 2026-09-17 20:50 UTCEG score recompute
  28. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  29. 2026-09-16 18:58 UTCEG score recompute
  30. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  31. 2026-09-16 05:15 UTCEG score recompute
  32. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  33. 2026-09-15 03:47 UTCEG score recompute
  34. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  35. 2026-09-13 17:03 UTCEG score recompute
  36. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  37. 2026-09-12 16:04 UTCEG score recompute
  38. 2026-09-11 15:01 UTCEG score recompute
  39. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  40. 2026-09-11 10:51 UTCEG score recompute
  41. 2026-09-10 09:43 UTCEG score recompute
  42. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  43. 2026-09-09 00:26 UTCEG score recompute
  44. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  45. 2026-09-07 19:11 UTCEG score recompute
  46. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  47. 2026-09-06 17:29 UTCEG score recompute
  48. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  49. 2026-09-05 16:25 UTCEG score recompute
  50. 2026-09-04 15:08 UTCEG score recompute
  51. 2026-09-04 06:46 UTCEG score recompute
  52. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  53. 2026-09-02 20:23 UTCEG score recompute
  54. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  55. 2026-09-01 16:37 UTCEG score recompute
  56. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  57. 2026-09-01 08:09 UTCEG score recompute
  58. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.3% · 27th percentile
  59. 2026-08-31 19:31 UTCEG score recompute
  60. 2026-08-31 18:57 UTCEG score recompute
  61. 2026-08-30 22:32 UTCEG score recompute
  62. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  63. 2026-08-30 01:42 UTCEG score recompute
  64. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.3% · 26th percentile
  65. 2026-08-28 20:25 UTCEG score recompute
  66. 2026-08-28 19:10 UTCEG score recomputeFirst assessed: 9.1 CRITICAL

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-55247?
CVE-2026-55247 is a critical-severity vulnerability; its CVE record was 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 the CVE record for CVE-2026-55247 published?
The CVE record for CVE-2026-55247 was published on August 28, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 9, 2026; the record at its source may have been updated since.
Is CVE-2026-55247 actively exploited?
CVE-2026-55247 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (36th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-55247?
CVE-2026-55247 has a CVSS base score of 9.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-55247?
A fix for CVE-2026-55247 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-55247 are linked in the Vendor Advisories panel on this page.

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