CVE-2026-18421

LOWPre-NVD 2.12.1—
EchelonGraph scoreMEDIUM confidence

This low-severity CVE scores 2.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (17th percentile of EPSS-scored CVEs). 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
Trending — 3 sources updated this week
2.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 2.1Exploit: None knownExposed services: Not assessed

No fix is confirmed yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for the fix.

Concrete CMS 9 through 9.5.2 does not perform an authorization check in three actions of the Boards data source dashboard controller (update, update_data_source, and delete_data_source), which resolve a ConfiguredDataSource directly from an attacker-supplied identifier without confirming the requester's edit permission on the owning board. A user granted edit_board_settings on a single board was therefore able to modify or permanently delete the configured data sources of any other board on the site, halting the affected board's content feed and resetting its custom weighting. The CSRF token that guards these actions was validated but bound to the action name rather than to the target object, so a token legitimately obtained for one board could be replayed against another board's ConfiguredDataSource identifier and did not constrain access. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 2.1 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N. Thanks Winston Crooker for reporting.

CVSS v3
2.1
EG Score
2.1LOWmedium confidence
EG Risk
10
EG Risk 10/100CISA SSVC

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
Severity21% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.
EPSS PROB
0.3%
EPSS %ILE
17th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines, and watch the vendor's advisory for the fix.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 15, 2026

Last Modified

September 16, 2026

References (1)

Vendor Advisories for CVE-2026-18421(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 10× in last 7d / 29× 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. 2026-10-04 23:21 UTCEPSS rescore
  2. 2026-10-03 14:25 UTCEPSS rescore
  3. 2026-10-03 05:43 UTCEG score recompute
  4. 2026-10-03 05:43 UTCGHSA enrichment
  5. 2026-10-01 19:49 UTCEPSS rescore
  6. 2026-09-30 15:02 UTCEPSS rescore
  7. 2026-09-30 11:57 UTCEG score recompute
  8. 2026-09-30 11:57 UTCGHSA enrichment
  9. 2026-09-29 15:20 UTCEPSS rescore
  10. 2026-09-28 13:51 UTCEPSS rescore
  11. 2026-09-27 18:14 UTCEG score recompute
  12. 2026-09-27 18:14 UTCGHSA enrichment
  13. 2026-09-27 13:47 UTCEPSS rescore
  14. 2026-09-26 15:58 UTCEPSS rescore
  15. 2026-09-25 00:32 UTCEG score recompute
  16. 2026-09-25 00:32 UTCGHSA enrichment
  17. 2026-09-22 06:49 UTCEG score recompute
  18. 2026-09-22 06:49 UTCGHSA enrichment
  19. 2026-09-19 13:06 UTCEG score recompute
  20. 2026-09-19 13:06 UTCGHSA enrichment
  21. 2026-09-18 19:27 UTCEPSS rescore
  22. 2026-09-16 19:23 UTCEG score recompute
  23. 2026-09-16 19:23 UTCGHSA enrichment
  24. 2026-09-16 14:07 UTCEPSS rescore
  25. 2026-09-15 20:40 UTCEG score recompute
Show 4 more
  1. 2026-09-15 19:48 UTCEG score recompute
  2. 2026-09-15 19:32 UTCEG score recompute
  3. 2026-09-15 19:13 UTCEG score recompute
  4. 2026-09-15 19:12 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-18421?
CVE-2026-18421 is a low vulnerability published on September 15, 2026. Concrete CMS 9 through 9.5.2 does not perform an authorization check in three actions of the Boards data source dashboard controller (update, updatedatasource, and deletedatasource), which resolve a ConfiguredDataSource directly from an attacker-supplied identifier without confirming the…
When was CVE-2026-18421 disclosed?
CVE-2026-18421 was first published on September 15, 2026, with the most recent update on September 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-18421 actively exploited?
CVE-2026-18421 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (17th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-18421?
CVE-2026-18421 has a CVSS base score of 2.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-18421?
No fix for CVE-2026-18421 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. The vendor advisories EchelonGraph has for CVE-2026-18421 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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